Amazon.com: Cheerwing 4-in-1 Charger & 4pcs 3.7V 350mAh Rechargeable Lipo Battery for Cheerwing UDIRC U12S U12 : Toys & Games
SM2P 3.7V Charger Cable 1S USB Battery Charger with SM-2P Connector – URGENEX RC Hobby
Tenergy Charger for 3.7V DC Li-ion Battery - Tenergy
How to Make 3.7V Battery Charger At Home - YouTube
Adafruit Universal USB / DC / Solar Lithium Ion/Polymer charger [bq24074] : ID 4755 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits