Lepow via eBay offers its Lepow Moonstone 6,000mAh External Battery Pack in Black, model no. L-MS6000-Black-US-01-FBA, for $15.99 with free shipping. That's tied with last month's mention of the battery pack in another color and the lowest total price we've seen. (It's a current low by $44.). It features two USB ports and is compatible with most smartphones and tablets.