I liked the original design that much, but I need a case for 2 and 4 batteries, so I decided to remodel the original case in Fusion 360 and adjusted the case to my needs.

Maybe you need smaler cases than the original 6x 18650 box like me, here are two new versions with space for 2 and 4 18650 batteries.

For the hinge you just need a piece of fillament.