Lithium Ion Polymer Battery with Short Cable - 3.7V 420mAh : ID 4236 : $6.95 : Adafruit Industries, Unique & fun DIY electronics and kits
UL Approved Lithium Ion 18650 3.7V 2000mAh Cylinder Rechargeable Battery with High Power - China Lithium Battery and Rechargeable Battery price | Made-in-China.com