TL;DR:

• Change the value nodeport.enabled to true inside cp-kafka/values.yaml before deploying.
• Change the service name and ports in you TCP NGINX Configmap and Ingress object.
• Set bootstrap-server on your kafka tools to <Cluster_External_IP>:31090

Explanation:

The Headless Service was created alongside the StatefulSet. The created service will not be given a clusterIP, but will instead simply include a list of Endpoints. These Endpoints are then used to generate instance-specific DNS records in the form of: <StatefulSet>-<Ordinal>.<Service>.<Namespace>.svc.cluster.local

It creates a DNS name for each pod, e.g:

[ root@curl:/ ]$ nslookup my-confluent-cp-kafka-headless
Server:    10.0.0.10
Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local

Name:      my-confluent-cp-kafka-headless
Address 1: 10.8.0.23 my-confluent-cp-kafka-1.my-confluent-cp-kafka-headless.default.svc.cluster.local
Address 2: 10.8.1.21 my-confluent-cp-kafka-0.my-confluent-cp-kafka-headless.default.svc.cluster.local
Address 3: 10.8.3.7 my-confluent-cp-kafka-2.my-confluent-cp-kafka-headless.default.svc.cluster.local

• This is what makes this services connect to each other inside the cluster.

I've gone through a lot of trial and error, until I realized how it was supposed to be working. Based your TCP Nginx Configmap I believe you faced the same issue.

• The Nginx ConfigMap asks for: <PortToExpose>: "<Namespace>/<Service>:<InternallyExposedPort>".
• I realized that you don't need to expose the Zookeeper, since it's a internal service and handled by kafka brokers.
• I also realized that you are trying to expose cp-kafka:9092 which is the headless service, also only used internally, as I explained above.
• In order to get outside access you have to set the parameters nodeport.enabled to true as stated here: External Access Parameters.
• It adds one service to each kafka-N pod during chart deployment.
• Then you change your configmap to map to one of them:

data:
"31090": default/demo-cp-kafka-0-nodeport:31090

Note that the service created has the selector statefulset.kubernetes.io/pod-name: demo-cp-kafka-0 this is how the service identifies the pod it is intended to connect to.

• Edit the nginx-ingress-controller:

- containerPort: 31090
  hostPort: 31090
  protocol: TCP

• Set your kafka tools to <Cluster_External_IP>:31090

Reproduction: - Snippet edited in cp-kafka/values.yaml:

nodeport:
  enabled: true
  servicePort: 19092
  firstListenerPort: 31090

• Deploy the chart:

$ helm install demo cp-helm-charts
$ kubectl get pods
NAME                                       READY   STATUS    RESTARTS   AGE
demo-cp-control-center-6d79ddd776-ktggw    1/1     Running   3          113s
demo-cp-kafka-0                            2/2     Running   1          113s
demo-cp-kafka-1                            2/2     Running   0          94s
demo-cp-kafka-2                            2/2     Running   0          84s
demo-cp-kafka-connect-79689c5c6c-947c4     2/2     Running   2          113s
demo-cp-kafka-rest-56dfdd8d94-79kpx        2/2     Running   1          113s
demo-cp-ksql-server-c498c9755-jc6bt        2/2     Running   2          113s
demo-cp-schema-registry-5f45c498c4-dh965   2/2     Running   3          113s
demo-cp-zookeeper-0                        2/2     Running   0          112s
demo-cp-zookeeper-1                        2/2     Running   0          93s
demo-cp-zookeeper-2                        2/2     Running   0          74s

$ kubectl get svc
NAME                         TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)             AGE
demo-cp-control-center       ClusterIP   10.0.13.134   <none>        9021/TCP            50m
demo-cp-kafka                ClusterIP   10.0.15.71    <none>        9092/TCP            50m
demo-cp-kafka-0-nodeport     NodePort    10.0.7.101    <none>        19092:31090/TCP     50m
demo-cp-kafka-1-nodeport     NodePort    10.0.4.234    <none>        19092:31091/TCP     50m
demo-cp-kafka-2-nodeport     NodePort    10.0.3.194    <none>        19092:31092/TCP     50m
demo-cp-kafka-connect        ClusterIP   10.0.3.217    <none>        8083/TCP            50m
demo-cp-kafka-headless       ClusterIP   None          <none>        9092/TCP            50m
demo-cp-kafka-rest           ClusterIP   10.0.14.27    <none>        8082/TCP            50m
demo-cp-ksql-server          ClusterIP   10.0.7.150    <none>        8088/TCP            50m
demo-cp-schema-registry      ClusterIP   10.0.7.84     <none>        8081/TCP            50m
demo-cp-zookeeper            ClusterIP   10.0.9.119    <none>        2181/TCP            50m
demo-cp-zookeeper-headless   ClusterIP   None          <none>        2888/TCP,3888/TCP   50m

• Create the TCP configmap:

$ cat nginx-tcp-configmap.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: tcp-services
  namespace: kube-system
data:
  31090: "default/demo-cp-kafka-0-nodeport:31090"

$ kubectl apply -f nginx-tcp.configmap.yaml
configmap/tcp-services created

• Edit the Nginx Ingress Controller:

$ kubectl edit deploy nginx-ingress-controller -n kube-system

$kubectl get deploy nginx-ingress-controller -n kube-system -o yaml
{{{suppressed output}}}
        ports:
        - containerPort: 31090
          hostPort: 31090
          protocol: TCP
        - containerPort: 80
          name: http
          protocol: TCP
        - containerPort: 443
          name: https
          protocol: TCP

• My ingress is on IP 35.226.189.123, now let's try to connect from outside the cluster. For that I'll connect to another VM where I have a minikube, so I can use kafka-client pod to test:

user@minikube:~$ kubectl get pods
NAME           READY   STATUS    RESTARTS   AGE
kafka-client   1/1     Running   0          17h

user@minikube:~$ kubectl exec kafka-client -it -- bin/bash

root@kafka-client:/# kafka-console-consumer --bootstrap-server 35.226.189.123:31090 --topic demo-topic --from-beginning --timeout-ms 8000 --max-messages 1
Wed Apr 15 18:19:48 UTC 2020
Processed a total of 1 messages
root@kafka-client:/# 

As you can see, I was able to access the kafka from outside.

• If you need external access to Zookeeper as well I'll leave a service model for you:

zookeeper-external-0.yaml

apiVersion: v1
kind: Service
metadata:
  labels:
    app: cp-zookeeper
    pod: demo-cp-zookeeper-0
  name: demo-cp-zookeeper-0-nodeport
  namespace: default
spec:
  externalTrafficPolicy: Cluster
  ports:
  - name: external-broker
    nodePort: 31181
    port: 12181
    protocol: TCP
    targetPort: 31181
  selector:
    app: cp-zookeeper
    statefulset.kubernetes.io/pod-name: demo-cp-zookeeper-0
  sessionAffinity: None
  type: NodePort

• It will create a service for it:

NAME                           TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)             AGE
demo-cp-zookeeper-0-nodeport   NodePort    10.0.5.67     <none>        12181:31181/TCP     2s

• Patch your configmap:

data:
  "31090": default/demo-cp-kafka-0-nodeport:31090
  "31181": default/demo-cp-zookeeper-0-nodeport:31181

• Add the Ingress rule:

        ports:
        - containerPort: 31181
          hostPort: 31181
          protocol: TCP

• Test it with your external IP:

pod/zookeeper-client created
user@minikube:~$ kubectl exec -it zookeeper-client -- /bin/bash
root@zookeeper-client:/# zookeeper-shell 35.226.189.123:31181
Connecting to 35.226.189.123:31181
Welcome to ZooKeeper!
JLine support is disabled

If you have any doubts, let me know in the comments!