Since 12" circulars can be a wee bit difficult to find, I thought I'd post some of the sources I came across:
Addi 12" from Pacific Wool & Fiber - $14.95
Addi 12" from Handknitting.com - $13.50
Clover plastic 12" (on eBay) - $4.45 - note, these are marked US8, but run small according to the seller, so I'm assuming US8 = US7-ish
Clover plastic 12" from Worldknit.com - this store also has 8.25" circulars! Same caveat applies re: size, I'm assuming.
Of course, you can use DPNs, but the circulars go faster. Plus, if you're making the legwarmer pattern, which I calls for US 8, you could probably get by with using the same needles, thereby getting at least one more project out of them. I went with the Clovers. Has anyone else tried them? Are they indeed about a US7? Any other needle experiences to share?
EDIT (1/29/05): I asked the eBay seller I bought the 12" Clovers from, and she says the size 8s also say "4.5mm" on the package, which would make them equivalent to a US7.