I originally saw this box in a post from Matterhackers, but there was no link to an STL.  After a pretty exhaustive search, I couldn't find it, so I took to Fusion360 and designed my own.

Any material can be used as long as 0.2mm layer height is used (which is important to get the strap thickness correct).  The inside dimensions of the boxes are included in the name and all are 19mm tall (inside).

These boxes weren't designed for anyting specific, I just thought they were fun and cool.

Have fun with them!