Hello,

If you're looking for "instant gratification" to just warm your fingers, perhaps a reasonably good ceramic heater that plugs into the cig. lighter (or can be wired of course) is what you might want if you don't want a lot of fuss. I had one for years as a poor substitute for my busted heating system. They are not really an acceptable replacement for a bad stock heater, but good ones can make a handy hand heater. The one I used to have had a little fan and heater in the back for just this purpose. And when winter is over, just remove the thing. Perhaps not the most elegant solution, just a thought...

Good luck!