Jensen entered and exited the US market before TSBs were commonplace.

Since the clubs for most of the Jensen models stateside are defunct, your friend's best bet is a specialist consulting firm. The first one that comes to mind (Interceptor models only) is K&D Enterprises.

Their help is not free but reasonably priced. If your friend is somewhat organized, has a vision of his final goals is flexible and realistic, the proprietor can be of great help.