Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Most USB car chargers do the job,but try to get a high capacity one,especially if you want it to charge other devices too. I bought one that charge two phones or other USB devices at the same time in a local car part store.
 
Kenu Dualtrip.

51GinbXSryL._SX522_.jpg

"Dualtrip, the ultimate charger, features two, side–by–side high–speed USB ports capable of simultaneously charging two smartphones or tablets at full speed. Its elongated shape is engineered to stay cool and safely prevent overheating while outputting 2.4 amps from each port, making it the fastest way to charge your gadgets."

P:S.:
Worth having a look at Kenu Car Kit Deluxe as well.

5271601_sa.jpg
 
I think Anker is the best recommend for car charger, and I also find the vodool car charger is a good choose, both can find on amazon.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.