Lithium Ion Polymer Battery - 3.7v 500mAh : ID 1578 : $7.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Rechargeable 3.7V 2200mAh Lithium ion battery 3.7V Li ion cells for 11.1V 12V 24V Singing machine mobile DVD player|Rechargeable Batteries| - AliExpress
Amazon.com: 4 Pcs ICR 10440 Rechargeable Lithium Ion Battery,3.7v Batteries 350mAh (0.39 * 1.73 inch, Shorter Than AAA Size) : Health & Household
Amazon.com: Battery Packs Lithium Ion Battery Pack 3.7V 4400 mAh : Health & Household