Amazon.com: Lithium Rechargeable Battery Pack for Both Xbox Series X|S and Xbox One/S/X/Elite/Elite 2 Controller; Plug Play and Charge Kit; Charging Status LED; Long Life; Quick Charge; 2 Sets for 2 Controllers :
Kastar Ni-MH 1.2V 2200 mAh High Power Battery for NiCD Paper Wrapped Sub-C Cell | eBay