If you're into DIY, you could roll your own. The Nokia 900 Qi charger input is 12VDC, so wiring it into your car is trivial. I did it, and it works great!

Note that I linked to the 901 pillow charger, because it is cheap right now. Rest assured, it is a 900 stuffed in a little pillow. It will work just fine for tearing apart and repurposing.