Amazon.com: SPARKOLE 7.4V 2500mAh Li-ion Rechargeable Battery for Speaker/Remote Control Toy/Bluetooth Boom Box/Portable DVD Player/Outdoor Lighting : Toys & Games
Lithium Ion Polymer Battery - 3.7v 2500mAh : ID 328 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits