Lithium Ion Polymer Battery - 3.7v 500mAh : ID 1578 : $7.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Amazon.com: HXJNLDC DC 3.7V 2100mAh 654060(704060) Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Product, Mobile Energy Storage Power Supply. : Electronics
Amazon.com: Tikom 3200mAh Li-ion Replacement Battery, Only for G8000Pro Robot Vacuum : Home & Kitchen