Hi Patrick
I have made a number of castings for broken non ferrous parts with the following product. Search online for Alumilite. It is a wonderful product and a lifesaver. In a nutshell it comes as a whole kit with everything needed to make a part. You make a soft negative mold and then mix and pour the Alumilite in it, let it harden, peel off the mold and there you have it a perfect copy. You can make a piece to fit the broken spot or cast a whole grip panel. If you do, I would suggest cleaning up the broken area to a more regular shape and then getting molding clay. Brownells sells this. It is a wonderful product as it will harden after molded into place. I have used Alumilite to repair grips, butt plates, and forend pivots on old wall hanger shotguns after carving out a perfect wood replacement and then using Alumilite to mold a replacement part.
You can search for Alumilite online but I’ve also seen it on Amazon. It’s worth it and at $30 – 50 it won’t break the bank. It will also give you another skill set to put in your tool kit.
Good luck.
