Amazon.com: iFixit Battery Compatible with Nintendo Wii U Gamepad : Video Games
KMD Wii U Gamepad Internal Expended Battery Pack 3000MaH for Wii U Gam – Gametronex.com
I bought the extended Gamepad battery. I see Nintendo planned a spot for it all along. : r/wiiu
Wii U Controller - 10,000mAh Internal Battery Mod | GBAtemp.net - The Independent Video Game Community
Wii U GamePad battery life gets a boost from new Nyko accessories - Polygon
Comparing all three batteries for the Wii U Gamepad - YouTube
Amazon.com: Battery Replacement Rechargeable Battery Pack for Wii U Gamepad, 3600 mAh Battery for Nintendo Wii U Gamepad Remote Controller : Video Games