DailySale offers the Liger 5,200mAh Dual USB Portable Battery Pack in Black or White for $17.99 with free shipping. (Liger Electronics via Amazon has it in five colors for a buck more.) That's $42 off list price and the lowest total price we could find. It features an LED power indicator.
Note: The countdown timer on the product page does not reflect an actual expiration time and resets daily.