As one of its daily deals, Amazon offers Prime members the PNY M3000 3,000mAh 1-amp Portable Battery Charger, model no. P-B-3000-M-K01-RB, for $12.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $8.) That's the lowest total price we could find by $10 and a very strong price for a name-brand power bank. It features a built-in microUSB cable for charging. (It also has a USB port for charging other devices with a separate cable.) Deal ends today.