Has anyone tried heated insoles? They're insoles that have some sort of chemical that heats up when you activate them. Just drop them in your shoes, and you're good to go. They're similar to the hand-warmers skiiers and hunters use. They last about 6 hours. You can pick them up at wal-mart for about 2.00 a pair. I use them in my workboots and I've always been a happy camper in the cold. You can find them cheaper by shopping around, but the link below is what they look like.
http://www.fogdog.com/sm-grabber-hea...i-1442700.html