Amazon.com: Replacement Battery for iPod Nano 2 2nd gen Generation 2GB 4GB 8GB Model A1199, with Easy Tools : Electronics
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
Amazon.com: iFixit Battery Compatible with iPod Nano Gen 2 : Electronics
Original Battery For Ipod Nano 1 2 3 4 5 6 7 4th 5th 6th 7th 1st 2nd Generation 2 Gen 2gen 3rd 3 Gen 3gen + Free Tools - Mobile Phone Batteries - AliExpress