iPod classic 160gb modded to 256gb with 2000mah battery and Bluetooth. Just waiting on a 3d printed back. All fits within a thin shell. Very happy with how it's come up. :
iPod Video High Capacity Replacement 3000mAh Battery 5th/5.5 Generation 5G
3rd party extended Battery guide – iFlash.xyz
Amazon.com: M-Player Compatible with iPod Classic Video 5th gen 256gb Upgraded 2000mAh Battery Transparent : Electronics
Amazon.com: Custom 1TB SSD with 3000mAh Battery Upgraded Compatible for iPod Classic 7th Generation 1TB (RED) : Electronics
1 X 3000mah Ssd Hd Upgrade Battery For Ipod 5th Gen Video 30gb Ipod 6th Gen Classic 80gb 120gb 7th Gen 160gb + Repair Tools Kit - Mobile Phone Batteries - AliExpress
3rd party extended Battery guide – iFlash.xyz
iPod Classic new Battery & 256GB SD Card: still works in 2022! - YouTube
iPod Classic 5th Gen Battery Replacement | iMaster Repair
How to upgrade an iPod for 2018 with flash memory and a new battery - The Verge
LG 3800mAh Battery Upgrade replacement for iPod Classic 6 6.5 7 Video 5 5.5 Thin | eBay
Modding an iPod Classic - 1 TB and bigger battery
NewerTech 540mAh NuPower Battery for Apple iPod 5th Gen & Classic
Upgrading my iPod Video with a T H I C C 1950mAh battery (and other stuff) - YouTube
Giving A 6th Generation IPod A New Lease On Life | Hackaday
2XLG3800mAh Battery Upgrade replacement for iPod Classic 6th 7th Video 5th Thin | eBay
Amazon.com: MaximalPower™ Replacement Battery for Apple iPod Video/Classic 30GB : Electronics
Amazon.com: Replacement for Apple 616-0229 iPod Classic 80GB iPod Classic 120GB iPod Video 30GB 616-0230 iPod Classic 6th GEN A1238 80GB iPod Classic 6th GEN MB029 80GB Battery : Electronics