The ones I have seen are blue or red, or painted blue or red and made of hard rubber (I think). Maybe they were used as training tools as well? Are these available for purchase at all? Where did the ones that are out there come from? I have done a bit of looking, and come up empty.

"Blue Guns" are used for training. I don't know about using them as a mould.

http://www.ondutygear.com/brand-rings-blue-guns.html

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That's great! Thanks for the link s&wchad. That will take care of the J Frame. Now if I can find a 2" K Frame RB, I will be in business.

ASP makes a K frame but it's 4" square butt. You might try these folks, they make the aluminum models.
http://www.duncansoutdoor.com/

Thanks for the link jellybean. I know a 2" RB K Frame was made at one time. There is a guy on everyones favorite auction site that sells a lot of holsters. He shows the holsters with these training replicas. I purchased a holster from him, and the replica in the photo was a 2" RB K Frame. There are probably a lot of them rattling around in some forgotten box in a police storeroom somewhere.

The holstermakers use, I think, cast aluminum gun shapes to mold and bone shape, or at least that's what I've seen in their shops. The blue or red plastic guns are training simulations. I think a diligent web search will find a source for the metal molding positives...