expertbattery via eBay offers a 10,400mAh Power Bank Battery Pack in Black for $19.99 with free shipping. That's $10 under the lowest total price we could find for a similar battery pack elsewhere, although we saw it for a buck less in September. It features 1A and 2A dual USB output and a built-in microUSB cable. It works with iPod, iPhone, smartphones, digital cameras, and other devices.