Lithium Ion Battery - 3.7V 2000mAh : ID 2011 : $12.50 : Adafruit Industries, Unique & fun DIY electronics and kits
Amazon.com: URGENEX 7.4V Li-ion Battery 2000mAh 2S Battery with SM 2P Plug High Capacity for Remote Control RC Boat 2 Pack H101 RC Batteries with 2 USB Chargers : Toys & Games
Amazon.com: EEMB Lithium Polymer Battery 3.7V 2000mAh 103454 Lipo Rechargeable Battery Pack with Wire JST Connector for Speaker and Wireless Device- Confirm Device & Connector Polarity Before Purchase : Health & Household