Simple user database / LDAP lookup options for containers

In my environment we launch containers with a specific uid/gid that our users use as workspaces. It's a bit finicky and one of the drawbacks is that there won't be a matching user in /etc/passwd, causing all kinds of havoc. I was thinking of just maintaining a shared /etc/passwd, storing it in a secret file and then mounting on top of the container's file. The above approach doesn't seem very robust, so I looked into other nss option such as sssd. We have AD setup so integrating with that would be ideal. After some research I found that sssd is not easy to setup within a container and is meant to be run with root privileges so it may be a dead end. Are there any other more lightweight alternatives for our use case? We don't really need authentication just the ability to do LDAP lookups for uid/gids.