Replaced the dead battery in an old iPod Nano I bought (really wanted a cheap Product Red one) and not even 2 days later the replacement battery expanded. I would call this
Replacement batteries for Apple's iPod Classic, iPhone, Touch, Mini, Nano, 1st Gen, 2nd Gen, 3rd Gen, 4th Gen, and Video | iToolBatteryKit
Battery for Apple iPod A1199 Nano 2nd Generation Gen 616-0311 2gb 8gb MA725LL/A | eBay
Fixing My Dad's 2nd Gen iPod Nano! (Battery Replacement Tutorial) - YouTube
Internal Battery Pack for Apple iPod Nano 2
Replacement iPod Nano 2nd Generation Battery 400mAh 616-0282 A1199 Fast Post | eBay
Battery 400 mAh for iPod Nano 2G | Sintech-Shop - Spare parts for mobile phones, game consoles and more
Apple iPod Nano 2nd Generation. High capacity 370 mAh Li-ion battery