Bone Clones, Inc. (http://www.boneclones.com/)
21416 Chase Street #1
Canoga Park, CA 91304
Phone: 818-709-7991 or 800-914-0091
Fax: 818-709-7993

Evolution Store, The (http://www.evolutionnyc.com/)
120 Spring Street
New York, NY 10012
Phone: 800-952-3195
Fax: 212 343-1815

Grey Owl (http://www.greyowlcrafts.com/)
502 Atkins Avenue
P.O. Box 1185
Neptune, NJ 07754-1185
Phone: 800-487-2376 or 732-775-9010 (Monday thru Friday - 9am-5pm EST)
Fax: 732-774-9330

Jonas Taxidermy Supply Company (http://www.jonastaxidermy.com/)
1850 Dogwood Street
Louisville, CO 80027
Phone: 1.800.525.6379 or 303.466.1112
They have a massive warehouse full of high-density foam models of just about every animal on Earth, and they're moderately priced (though their full-size bull elephant model is the most expensive :) .. but I get zebra models and such from them for around $65 for a full shoulder mount (shoulders, neck, full head). These models can then be modified with clay as needed or used directly in casting, or sew your cloth to fit it, or whatever. I visited their factory and they gave me a full tour… nifty stuff, and they had a bundle of techniques and suggestions once I told them what I was doing.
The models pretty much all show some of the musculature which is nice, and you can see the details if you contact them and they'll send you a free, thick, full color catalogue. They have just about everything you'll want to use.

Lone Star Taxidermy Supply Co. (http://www.lonestartaxidermy.com/)
632 5th Ave. North
Texas City, TX 77590
Phone: 409-948-2673
Orders: 1-800-347-5009 (Mon-Fri 8:30am-4:30pm CST)

Tandy Leather Company (http://www.tandyleather.com/)
PO Box 791
Fort Worth, TX 76101
Phone: 800-433-3201 (Mon-Fri 8am-6pm CST)
Fax: 817-496-9806

Tohickon Glass Eyes (http://www.tohickonglasseyes.com/)
15 Geigel Hill Road
Erwinna, PA 18920
Phone: (610) 294-9483 or 1-800-441-5983 (Mon-Fri 9am-5pm EST)
Fax: (610) 294-9487
According to Aetobatus, they sell all sizes and types of glass eyes in various styles and animal types, including birds and reptiles. They've also got prosthetic eyes, though not for human use. There is a $15 minimum order. Nothing is over $75.

Van Dyke's Taxidermy Supply (http://www.vandykestaxidermy.com/)
PO Box 278
39771 S.D. Hwy. 34
Woonsocket, SD 57385
Phone: (605) 796-4425 or 1-800-787-3355
Fax: 605-796-4085
Besides the usual assortment of jaws, teeth, and related, they also sell some good quality synthetic fur.

Wakeda (http://www.wakeda.com/)
PO Box 2114
Oakdale, CA 95361
Phone: (209) 848-0711

Taxidermy Net - http://www.taxidermy.net
The main site, where you can find links to other taxidermy companies. There's so many companies, that none can be adequately covered here in this FAQ. Here is a listing that gives you everything you want to know, and then some.