well, not sure that these would work while driving but here's a post I made earlier this month.

I thought I would share... I found these things called Hot Booties at walmart for $14.88, I just tried them and I'm in love! Pop them in the microwave for 30-60 seconds and you're good to go. Winter might be slightly better. Now we just need to design some fingerless gloves that go all the way up your forearm, made the same way.

If nothing else perhaps you could put little hotties (I think that's what they're called) sometimes used for camping. Maybe you could stick one in your shoe before you leave work?

I suffer from the cold feet of CRPS. It's awful isn't it? So sorry hon. Hope you find something that works.