Amazon.com: 18650 to 21700 Battery Adapter, Converter Adapter for 21700 Flashlight Cases with Metal Contacts 18650 Sleeve Batteries Protective 21700 Battery Adaptor Holder Accessories (2 Battery Converters) : Electronics
Amazon.com: 18650 to 21700 Battery Adapter, Converter Adapter for 21700 Flashlight Cases with Metal Contacts 18650 Sleeve Batteries Protective 21700 Battery Adaptor Holder Accessories (5 Battery Converters) : Electronics
Amazon.com: XTAR VC4 Plus Battery 3A Fast Charger, 4 Bay Rechargeable Battery Charger Extend Version for 3.6V 3.7V 18650/20700/21700 Li-ion IMR INR ICR for 1.2V AAA SC Ni-MH Ni-CD with QC3.0 Adapter :
18650 Battery Adapter For 20700 / 21700 Mods - iVapour
Diy Usb Power Bank Kit Box Case 18650/18700/20700/21700 Battery Charger Adapter Battery Pack For Iphone Android Bank Case Box - Battery Accessories & Charger Accessories - AliExpress