Amazon.com: 18650 Battery Charger, 2 Bay Smart Universal USB Battery Charger for 3.7V Rechargeable18650,26650, 18500, 17335, Ni-MH Ni-Cd A AA AAA IMR Batteries,Power Bank (Batteries not Including) : Electronics
Lithium Inr 18650 4000mAh 3.7V 1s2p Li Ion Battery Pack - China Lithium Battery and 3.7V Li Ion Battery
Bulk Battery | Wholesale 18650, 21700 Lithium Ion Batteries
Fenix Rechargeable 21700 Li-ion Battery - 4000mAh - Fenix Store
List of tested batteries
Factory Price Customized 18650 Lithium Ion Battery 4000mAh 1s2p 3.7V Li on Battery Pack with PCM Wires Connector Deep Cycle - China 18650 Lithium Battery and 3.7V Lithium Battery