Found this car charger for the transformer. 12.0V at 2.0A. Does not come with a cord. Have to use original Asus charging cable. I ordered one. Will post again when I try it out.
I grabbed one of these guys on eBay for $14. It supposed to be custom made for the Transformer series tablets, and has a female USB connection so you just plug in you Asus charging cable.
be careful with car cargers, the electronic inside must be good quality or very soon the start-stop engine scycle will damage the charger or/and the tablet