App transfer from agency to client including paid plugins


I have an agency account and am in the process of moving a client app to their account. On a previous client development, I tried to use the “transfer” button and lost access to the App as an agency. So this time I tried adding the client email/account as a collaborator but the issue now is that paid plugins say they require payment again!

What is the correct way to do an App transfer from an agency to a client and still keep everything working?