Two companies currently make very high quality, full size polyurethane guns for law enforcement training. The companies are Blue Guns and ASP Red Guns. All models are around $40-$50 each. They each make Browning HPs:


IMHO, the Blue Gun is the closest: except for the hammer, it is virtually identical to one of the HPs documented to be used in Raiders. The Red Gun has the correct ring hammer, but the grip is wrong.
They don't make the big N-frame S&W, but they do make the slightly smaller but extremely similar K-frame replicas:


Again, I think the Blue Gun is the slightly better replica for our purposes, though both models have the thicker, non-tapering "bull" barrel which differs from Indy's tapered barrel Smiths.
I think these are some of the best options out there for holster stuffers. I will be ordering these sometime this summer, and will post a review.
RaiderZee