Find 'em at some of the fancier new associated supermarkets ("Morton Williams Associated") like the one at 57th and 7th. Also Rite Aid (believe it or not) is reputed to sometimes stock them. Supplies are by no means constant, but it's getting easier to find 'em. Look for the brown bag. They kill.
I'm reporting on this for Bloomberg this weekend, but wanted to give you guys a jump on it.