From Wikitech

kubernetes-client - Kubernetes client tools is the Debian package containing the Kubernetes client kubectl.

The Wikimedia APT repo provides a version maintained by User:Akosiaris. The same is true for kubernetes-master.

apt-cache show kubernetes-client

Package: kubernetes-client
Source: kubernetes
Provides: kubernetes-utils
Homepage: http://kubernetes.io/
Description: Kubernetes client tools
 Kubernetes command line utilities:
  * kubectl -- Kubernetes cluster management utility