Woot offers Aduro PowerUp Solar 6000mAh Dual USB Backup Battery- (Your Choice: Color) for $13.99 (orig. $79.99). Free shipping for Prime Members.

Product Description:
The PowerUp Solar Powered Backup Battery is the most convenient battery we've created, to date. No more having to remember to plug it in and charge it at night. Clip it onto your jeans, or your purse, and use it when you need it. The large solar panel on it will charge the device for you, giving you as much battery life as there is sunshine. With a 6000mAh capacity, you can get double the battery life of your mobile device. 

• Backup battery for smartphones or tablets
• Super-Fast charge 6000mAh capacity
• Dual USB ports: 1A and 2.1A
• Solar powered
• Easy to use; clip it onto jeans or purse, and use when needed
• Condition: new
• Product dimensions: 6” x 3.5” x 1”