Some C4S stores with at least one cockbiting video:

http://**********.com/41549/ - (Proper biting, chomping and wrenching, and those teeth look like fangs)

http://**********.com/60133/

http://********************/studio/32201

http://**********.com/23654

http://**********************9416 - (Clip I bought had good biting, shame there wasn't more)