Ebay offers 500,000mAh Portable Power Bank for $18 (reg $30) after code with free shipping.

Apply Code: DEALTWENTY

Product Description:
X-DRAGON Battery charger, power your life
X-DRAGON is founded by many young people who love modern life and challenge. With X-DRAGON power battery, you DO NOT need to worry your phones without power. We also focus on improving customers' shopping experience, go and enjoy the greatest happiness during the travel.
 
Palm Size--Fitting in the palm of your hand, this pocket-size portable charger lets you power your devices in any time
LCD Screen Display---never get caught off-guard, press the power button and see how much battery is left inside instantly
Wide Compatibility--Compatible with most USB-Charged devices such as iPhone, iPad, iPod, Samsung phones, other Android mobile phones, Kindles, Gopro Camera, GPS and More