Staying on the tangent, I thought of the same brand of chemical warmers that Spud mentioned, but I still have a good part of a box of about 40 of their hand warmers. Smaller than the foot ones, naturally, and cheaper too. They keep very well in your side bag or whatever, to be pulled out and dropped inside your glove (on the back of your hand side--they fit). They keep your hands warm all morning at least, and very well. My feet pretty much never get cold, but I'd see if I could get one of these into my boot too if they did. They wouldn't have to cover your whole foot, of course. If you warmed up one area, it would keep your whole foot much more comfy, and if they were too jammed in to walk comfortably, so what? You're riding, not walking. Good low-cost solution.