Who makes a good set of ivory polymer grips for a Beretta 84?

That's going to be hard to find. The 84 has been out of production for almost ten years. The big grip makers seem to be only doing 92 grips. I see a lot of various wood grips for the 84, but not much else.

This guy does a lot of custom work. You might want to give him a call:

https://hrvcustoms.com/beretta

Good luck with your search.

You might look at Lok grips. They have a few choices for the 81/84 pistols

Try Esmeralda.cc. She makes exotic grips.