RAVPower RP-PB04 Dynamo-On-the-Go 10000 mAh Power Bank for $17.80. Shipping is free on orders over $35. If needed, use this Filler Tool to pad the order for free shipping. Here is a screenshot for reference. It can provide an extra 45 hours of iPhone 4 movie time, 100% iPad 2, and 60% iPad 3 battery life. It also comes with various tips to work with Samsung, HTC, LG, Blackberry, Nokia, and other products.