Amazon.com: Winnerplusa Battery for iPhone 4 (3in 1) not Compatible with 4s : Cell Phones & Accessories
iContact iPhone 4/4S Battery Case - Black (IC-BC100)
Battery Replacement for Apple iPhone 4 / iPhone 4S Battery | eBay
Looking inside an iPhone 4/4S battery | Rip It Apart - Jason's electronics blog-thingy
Amazon.com: MFI-Apple Certified - ibattz Mojo Vogue Removable Battery Case for iPhone 4 and 4S White 1700mAhX2 fits all version of iPhone 4S/4 : Cell Phones & Accessories
Official iPhone 4 / 4S Battery Replacement Video & Instructions - iCracked.com - YouTube