Modify CLI prompt

I am trying to work out if there is a way to modify the TMSH CLI such that it applies to all users who login, without having to add a specific entry in the .conf file for each user.

We have a large number of users who access BigIP for various things, and users also come and go as well.

Has anyone achieved something like this? I want to add a label prior to username@hostname so users who are logged in are aware this is a test/prod instance.

Thanks.