MFI-Apple Certified - ibattz Mojo Vogue Removable Battery Case for iPhone 4 and 4S White 1700mAhX2 fits all version of iPhone 4S/4
Maxboost iPhone 4S Battery Case/iPhone 4 Battery Case (1900mAH, Fits All Versions of Apple iPhone 4 & 4S) - Detachable Battery Charger Case External Rechargeable Battery Pack Charging Power Case | Amazon
How to Replace the iPhone 4S Battery in 2 Minutes | DirectFix - YouTube