I don't think there ever were zigzag hand cranks, but there were a few early zigzag treadles in cabinets. I've seen Berninas, Neumans, Adlers, and a few others whith what looks like original 1950s cabinets, hand wheels and treadle setup. By the time zigzaggers became common treadle cabinets were hardly made anymore. For a hand crank, tell your friend they are practically all straight stitch models, but with the option of a zigzag attachment. I think the last hand cranks were Singer 201K23 and 185K, and those are oddities too. I doubt I will ever seen one first hand. There's just no point in converting a modern electric to hand crank?
A Singer 206, 306 and 319 might take a standard spoked wheel and hand crank, but I have never seen one. Perhaps someone on this forum can confirm it?