If you don't mind snail mail (and who does?), you could check out :
Phantom Video
P.O.Box 7301
Jupiter, Florida
33468-7301

They have rape videos, bestiality, incest, scatology and a seperate catalog for "mainstream" movies with bondage or S&M scenes (women in prison movies, prisoner of war films, that sort of thing). Prices aren't terrible -- about $69 for four tapes, postage included. They also have a phone number (what's the fun in that?): (561)747-9933.