inkcredibleprinting via eBay offers the 2,500mAh External Backup Battery Case for iPhone 4 / 4S in eight seven colors for $8.99 with free shipping. That's tied with our June mention and the lowest total price we've seen for a new 2,500mAh battery case for iPhone 4. (It's a current low for a comparable item by a buck.) It purports to provide an additional six to seven hours of talk time and an additional five days of standby. A screen protector is included.