toymodel55 via eBay offers this 1000mAh External Backup Battery for Apple iPhone / iPod in White (pictured) for $4.11 with free shipping. That's the lowest total price we could find in any color by $6, outside of the price below. It's compatible with Apple iPhone 3G, iPhone, iPod Touch, iPod Nano, iPod Classic, and iPod Video.

A close price: toymodel888 via eBay offers it in Black for $4.23 plus $0.35 for shipping.