You might try Territorial Seeds. In 2014 I grew peruvian purple fingerlings in a potato bag, but I was not really sold on those and will not grow them again. Territorial sells "OCA" -

Oca

Oxalis tuberosa Second only to potato cultivation in South America, Oca is a tuberous crop that is as diverse as it is curious. Oca has succulent, clover-shaped leaves on a compact, 10–12 inch tall plant that can spread 2–3 feet wide and tolerates a wide pH range. Grown and cultivated very similarly to potatoes, it prefers well-drained, fertile soil. Oca begins forming tubers in autumn. Sun dry the versatile tubers to bring out their sweetness. They can also be parboiled, roasted, baked, or served raw with salt, lemon and hot pepper sauce. It is nutritious; high in vitamins, minerals, protein and enzymes, and it's quick cooking. Can overwinter in zones 7 and above, or tubers can be dug and stored in a cool, frost-free place for planting in the spring. Oca is shipped as a plant at the end of April/beginning of May in 3 ½ inch pots. Complete growing instructions are included. Sorry, not available outside the contiguous US.

Thanks for the suggestion, I was looking at those but they're not quite what I was looking for. I may end up just buying some yellow potato seed and considering it good enough for now. All of the Peruvian purple potatoes seem to be sold out everywhere online. Bummer!