Lepow Official via Amazon offers Prime members the Lepow Impression Series 13,000mAh External Battery Pack in Blue, Green, or Ivory White for $27.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $5.82.) That's $61 off list and the lowest total price we could find. It features microUSB inputs and outputs, smart sleep mode, and four LED battery status indicators. It's compatible with a range of iOS and Android devices.