I don't know, but at work we get them from Full Circle Farms, an organic farm in Carnation. Maybe at a farmers' market? I'd suggest checking Pike Place, but I'm not sure I'd want to brave the Market on a Saturday for a less than sure thing.
I don't bother peeling them any more. Lately I've been slicing and roasting them, which of course makes practically every vegetable better! Note that they do go gray fairly quickly after they're cut, so you won't want to peel them ahead of time.
I bet if you were to place them in a bowl filled with water and a tad bit of buttermilk and salt that it would help to keep their color. A recipe I tried for banana blossoms suggests it. I bet it would work just as well, since it is probably an oxidizing situation.