eCase via Amazon offers the Kmashi 10,000mAh USB Power Bank for $13.99. Coupon code "USNL22D5" cuts it to $9.20. Plus, Prime members bag free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $6.52.) That's the lowest total price we could find by $7. It features dual-USB ports, four status LEDs, and compatibility with most USB-driven devices.