MGMike has a good point. I am sure you can find a someone, somewhere, with a CNC machine that has the skill set to scan the frame, write a program, and whittle one out of a billet of steel but Good Lord will that be expensive! You're talking Man with the Golden Gun expensive. I attached a link below; these boys may be a good place to start. They offer custom Beretta stuff and their work is top shelf. Good luck
@ Walther Wood: Thanks for the reply and for referring me to Wilson. Yes, I know it would be expensive to have it produced on a CNC machine. I'm hoping to find an old-school machinist who can cut it on a manual machine. The most complicated part of the build will be forming the magazine weld. The rest of the frame is very simple.