The whole thing is going to be too big to get inlaid on 1911 stocks. Maybe the bar on one side and the device of the other? (But I'm thinking the device is just going to be too big.)
Do a google search of makers and ask them if they will do a custom inlay/inlet job.
How much are you planning to shoot with the stocks once you get them? Anything that sticks above the surface is going to rub skin - usually in an unfriendly way. Unless it's going to be a BBQ gun I'd seriously think about having it set a tad deeper than the surface and then filling the gap with clear epoxy to mate with the surface of the rest of the stock.
As for the belt buckle - I'd start out knowing if you want the whole thing embedded in epoxy and then mounted to a buckle (the cheap & easy way IMHO) or if you want someone to cast a larger-than-life replica (enormously expensive). Folks that make rodeo buckles might be a good starting place for this project.