Three years ago I ordered two Niedzwetzkyana from Trees of Antiquity. In California. Only place I could find them at the time. High price. But great looking, healthy trees.
(One is now 15 to 20 feet tall…and one I potted up and planted the next year and it is still 5 feet tall and has had only one fruit thus far.) I would add…I planted the big one in a customer’s yard…so it’s not mine now. But I could probably find a couple little limbs I could snip and propagate on mine.)
You might try to find the REDFIELD apple…should be easier to find. It is bigger, juicier, and makes great cider all by itself I am told. (I’ve already pruned all I can from my Redfield…three short scions, two I am grafting and one I gave away already.)