Finding a real one is next to impossible. There are reproductions, but most of them are crap.
These folks have repros made especially for them. http://www.gun-parts.com/index.html/
I've been meaning to buy one and see if it's worth a flip, but haven't yet. Midway USA sells one, made by National. In the "customer ratings" it seems to get a solid 1 star out of a possible 5, so I'm staying away from those.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.