fix threaded valve stem

Thes shower handles will not turn the stems any more. They are 40 years old and I cannot find a replace ment for the handles which are stripped. I would like to keep them is there a fix for this i could use?

I was thinking a small amount of JB weld; I not sure if this is a good idea or not.

Surprisingly, there may well be handles available for your 40 year old shower. Could you post a picture?