StackSocial offers The Cable Key Charging Cable for iPhone 5 / iPad for $14.99 with free shipping. That's $25 off and the lowest total price we could find. Measuring the same size as a normal thumb drive, this key charger plugs into any USB port to charge compatible devices, including the iPhone 5 / 5S / 5C, iPad 4, iPad Mini, and iPad Air. Deal ends February 21.

Note that it is not MFI certified.