Rivendell usually carries them (
www.rivbike.com), but the shipping kills--it's like $7 minimum, so I usually just have them throw in a few dozen when I order something else.
I wonder if a local shop could order them for you from QBP or someplace. One of the LBS here has been good about stuff like that when I've needed it, and if they're ordering anyway, they'll probably cut you some slack on the shipping.