Amazon.com: Blomiky 2 Pack 3.7V USB Charger Cable with SM-2P Plug Connector for Mini RC Amphibious Stunt Car Boat Trucks 3.7V Li-ion and Li-Po Battery / 3.7V USB 2 : Toys &
EU 110V 220V Dual 81650 3.7V Battery Charger
Auto cut off 3.7 volt battery charger circuit - YouTube
Adafruit Universal USB / DC / Solar Lithium Ion/Polymer charger [bq24074] : ID 4755 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits