
There's tons of USB car chargers out there with multiple ports but not many can be had for this price. Right now you can grab an Omaker 3 USB port 5.1A car charger for just 5 bucks.
For the white model, enter 9ZSK7HVI at checkout to subtract $4 from the regular price. For black, you want SR3WKS5O.

Amazon.com Omaker Premium 3 USB 26W 5.1A Aluminum Panel Compact Designed USB Car Charger Black Cell Phones Accessories