Except for O. spinosa and thyrsifolia, none of the others ever ripened their seed in my old climate. Flowering was late, and hard frost too early. And of course one needs to have A LOT of plants to get even a tiny bit of well developed seed. So it took me quite a while to build up my stock of O. spinosa to have enough plants flowering each year to be able to offer even 30 packs of seed even in my own catalogue---and these always sold almost instantly.
I bought the cultivar Jade Mountain from Beavercreek Alpines and the remainder were grown from seed or trades through my former involvement in the Cactus and Succulent groups.