Lithium Ion Polymer Battery with Short Cable - 3.7V 350mAh : ID 4237 : $5.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Amazon.com: LCLEBM 3.7V 3800mAh USB Rechargeable Lithium Battery for Button Top with 2 in 1 Charge Cable for Flashlights, Camera, Headlamps, Doorbells, RC Cars (2 Pack) : Electronics
2-10PCS 1650mAh 3.7V 16650 Lithium ion Rechargeable Battery ICR16650 li-ion cell baterias for led flashlight digital device - AliExpress
Amazon.com: CWUU 18650 Rechargeable Battery Lithium 3.7 Volt Li-Ion Battery 3200mAh 3.7 Volt Rechargeable Battery 18650 Button Top Battery 2 Pack 0119 : Health & Household
Amazon.com: Rechargeable 3.7V Li Lipo Lithium Polymer Ion Battery Pack with 2 Pin 2.0mm/1.25mm JST Connector (502035 300mAh 2.0Jst) : Health & Household
5V 2A USB-C Type-c Fast Charger Module 3.7V 18650 Li-ion Battery DIY Power Bank | eBay