Gus Rentfro at Rio Bravo Reptiles does breed both Sonoran Desert Boas and Nicaraguan boas. At least he has in the past, and he always has excellent pure stock. You are unlikely to get a price quote, get on his mailing list and when there is something available you'll know. Tip, if he has something available that you like, buy it quick!
Also a good guy to talk to for any kind of info with boas. He's the ONE person I would consider an expert when it comes to raising and breeding boas, he knows how to do it with any subspecies and any locale.
Vin Russo at Cutting Edge Herpetological also breeds both locales. Again awesome pure stock. I have a possible super Hypo Sonoran from him.

Tom Burke works with Sonoran and Nicaraguan morphs. Don't know if you wanted only wild type or were okay with morphs of the locales.
Collette Sutherland from The Snake Keeper works with Nicaraguan and Sonoran stock as well.
The respective websites are:
www.riobravoreptiles.com
www.cuttingedgeherp.com
www.burkereptiles.com
www.ballpython.com
With Nics you have a number of morphs:
T-plus Albino
Type II Anery
Type I Anery
Inca
Hypo (and Super)
Ghost
Hypo Inca
There are also others but they are not pure Nicaraguan.
With Sonorans you have:
Hypos (and Supers)
Leopards, even the hets look different
Type II Anery
Albino (there have been 2, don't know what happened to them or where they are, there aren't any available yet though)
Keep in mind both Nics and Sonorans have been subjected to mixed breeding, especially with many morph projects. Nothing wrong with it as long as you properly represent them. I know I've got some mixed projects going this season. But if you are looking for pure, the 4 breeders I mentioned should be able to help you out and with TOP NOTCH stock.
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Gilbert Boas
The Boa List!