I had not considered that they could be purchased in a store - probably in the vegetable section? I'll have to check into that. From what I understand, you just need one eye off the tuber to grow a new plant, and there are many eyes on each tuber.
From what I understand, the Jerusalem Artichokes can be very invasive, so it's best to grow them away from your main garden or in big pots. I'm thinking of making a 4X4 raised bed just for a patch of them.
plant them near the lake and don't tell anyone. in the years to come it might become a reliable source of food. my mother had them growing wild by a creek with no attention at all.