With a rated capacity of 18.7Wh, 5200mAh at 3.6V, the Goal Zero Flip 20 packs a lot of power for its tiny size. Because of this, it's quickly become my favorite travel charger. It has a switchblade knife style USB connector for recharging in any USB port. I'm using it with the NomadKey Lightning to USB Cable.
Goal Zero Flip 20 $(removed) on Amazon