Amazon.com: HXJNLDC DC 3.7V 2100mAh 103450 Rechargeable Lithium ion Polymer Battery Replacement for PS4 Controller CUH-ZCT1 Series ,DIY 3.7-5V Electronic Product, Mobile Energy Storage Power Supply : Electronics
Lithium Ion Cylindrical Battery - 3.7v 2200mAh : ID 1781 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits