Cordovan is only processed by Horween in Chicago. It is from the rump of a horse. It's also a long and expensive process, but worth the effort. You would have to be a business and you would probably have to wait 6 months to get any from them. There are a few places you can find it including Brettuns Village and Seigal in California. Be careful though, there's probably more cordovan sold than what there has been processed.
The cost of 1st quality cordovan can be over $100.00 for less than 2 square feet. Lesser quality shells can purchased for less. At EFA we make cordovan tabs, and that's all that I use personally. It's natural, traditional, and superior to anything that I've tried.