Where to find and buy cold-hardy Russian variety rootstocks or seedlings for fruit?

I was inspired by this forum and some research to buy a bundle of Antonovka rootstock and grow them on for the trees themselves so that I could have a cold-hardy, reliable source of apples regardless of what modern taste says about the fruit. As I'm reading through this forum, I realize there are other varieties as well that have the potential for growing in the home orchard. I've learned of Duchess of Oldenburg/Borowinka for example.

Now, I understand the beauty of growing these from seed but I'm impatient and would like something with actual roots.

Does anybody know of any other cold-hardy varieties, probably Russian, that can be bought on the cheap in bulk and then grown on for their fruit?

Any online nurseries have these available?

Thank you!

I have been very happy with Fedco for rootstock and scion wood that I don't have.