The container-selinux package is available from the rhel-7-server-extras-rpms channel. You can enable it using:
subscription-manager repos --enable=rhel-7-server-extras-rpms
Sources for the package have been exported to git.centos.org, too, so you could rebuild it yourself using mock:
- https://git.centos.org/summary/rpms!container-selinux.git
(This is not a programming question, so you should use one of the other sites.)