I don't know of any strictly for Dealers, but I know that you can get wholesale pricing and support from
http://www.tirerack.com. I have done business with them at all 3 of the dealers I have worked for now, and have had an Excellent relationship with the same salesperson for almost 11 years now! I won't post a phone # on here, I don't want this to look like an ad, but I do HIGHLY recommend this company.