Amazon.com : PNGKNYOCN 8.4V Battery Pack Housing, with DC and USB Ports Waterproof and Safe Battery Pack Housing, Suitable for 2/4 x 18650 Rechargeable Lithium-ion Battery Bicycle Lamp Headlights and Mobile Phones :
8.4V 12800mAh 18650 Battery Pack 6 x 18650 lithium ion Rechargeable Battery Pack for Bike
Building an 8.4V Battery Pack: Step-by-Step Guide for Creating a Custom Power Solution - YouTube
Amazon.com : MinChen 8.4V Battery Pack Case for 2/4x 18650 li-ion Battery Waterproof Safety Cycling Battery Pack Case Box Cover with DC and USB Interface for Bike Light Headlamp Cell Phone, no
8.4V 18650 Waterproof Battery Pack Case 6 Pcs Batteries Holder Storage Box House Cover for Bicycle Bike Lamp - Walmart.com