ECK - How to set context path for elasticsearch?

After eck is setup, i can reach an index via http://quickstart-es-http/

How to set a custom context path so that the Elasticsearch is reachable via http://quickstart-es-http/customcontextpath/ ?

With standard Kubernetes services that's not possible afaik. But have a look at Ingress that should allow you to serve the Elasticsearch API from a subpath on your domain.