Some nurseries in my area carry a few common varieties but nonetheless are still very good. For atemoyas I'd go with either Geffner or African Pride. Cherimoya's I'd pick El Bumpo, Dr. White or Fino De Jete. Of course there's better varieties out there but you will have to find someone who grows them and can ship.

FYI, I have these varieties myself.

Armando, do you sell scions for all the Atemoya and Cherimoya trees you have available? I have a seed grown cherimoya tree and I have researched that when it starts to fruit, the fruit will not be true to the fruit I ate. I would like to try grafting some scions to the branches on my cherimoya tree.

Yes, Cherimoya can crossbreed with Atemoya. In fact Atemoya is actually a hybrid between Sugar Apple and Cherimoya.