Reaver, I too forget what they are called so I typed in "battery booster jump box with inverter."
What they are is a sealed cell that you can use like wall power or go for the usb charger because you will be in the same phase so no power lost to heat in the inverter.
JMac, that is the tree I was barking up. Depending on the amount of power needed to charge the battery in the Kindle you may be able to avoid buying a product that was made to meet someone else's needs. Hell you want to charge a kindle.. that sounds pretty easy.
Chesty, it is too easy. I will walk you though it. Find out about the battery.