Lithium Ion Cylindrical Battery - 3.7v 2200mAh : ID 1781 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Best 18650 Battery For Flashlight 3500mAh (Free Battery Case) Orbtronic
Amazon.com: FPVERA 3.7V 1200mAh Li-ion Battery 2PCS 3.7Volt Rechargeable Batteries with USB Charger Cable SM-2P Plug for RC Car Drift Monster Truck Off-Road Vehicle Remote Control Car High-Speed Climbing Racing : Toys
Lithium Ion Polymer Battery with Short Cable - 3.7V 420mAh : ID 4236 : $6.95 : Adafruit Industries, Unique & fun DIY electronics and kits