Design a USB adapter that supports 5v 2a.

I just bought a 2013 Explorer and took a trip and my wife was reading a book on a HP Touchpad and when the battery gave out at the end of 4 hours I tried to use the USB plug in the console and found out it would not charge the Touchpad.
It is designed for Apple proucts and ot powerful enough to support higher amperes.
I now will have to buy an inverter.