Here's a cheap power bank with a huge capacity (20000mAh): http://www.geekbuying.com/item/Original-ROMOSS-Sense6-Dual-USB-20000mAh-Power-Bank-Mobile-Power-Charger---White-362249.html
Use the coupon: 7ROMOSS1 to save $7 (USD).
Final price around CAD29 (depends on exchange rate).
Free shipping.
Picture:
http://i.imgur.com/j6cJ5Kp.jpg
