There are a number of large denture mills in Florence, South Carolina that take out alot of teeth... I had a classmate get some there. I'd recommend just hitting up 4-5 oral surgeons. You should be able to get a couple of good maxillary bicuspids for the posterior 2 canal tooth from ortho patients. Maxillary centrals are harder to get. I'd avoid any mandibular anterior, and maxillary molar (unless you enjoy finding MB1 and MB2). A maxillary central and an maxillary 1st bicuspid is ideal for wreb, with a second backup maxillary 1st bicuspid. I didnt have a backup max central in the endo mount since it would cause overlap of the mesial-distal radiograph shot they demand.
PS the endo models sucked when I took it in Spring 2004, beware of teeth popping out of the endo putty