I almost always carry my three flash drives on me that all have my projects and other irreplaceable data on them. I used to carry them in a small ziplock so that they would stay relatively dust and lint free, but that is not a sustainable solution since they wear through in the pocket in a few days.

I modeled this little clam shell case in Fusion 360, it has room for 3 normal sized thumb drives. There is a small piece of self adhesive foam weather stripping in the bottom half under each drive, and the dimensions are such that while closed that will hold a flash drive quite securely. The closure is accomplished with 2 pairs of 12x3mm neodynium magnets epoxied in the cutouts in the corners. N52 magnets are actually a bit much, as it is pretty difficult to open.

The hinge bore is 4mm, I did not have any 4mm rod handy though, so what I did was drilled the outer half of the hinges to 7/64" and then tapped the inner part #8-32. Two socket head cap screws with loctite thread locker are acting as a hinge.

I printed in PETG with a 1mm nozzle and .4mm layer height, 20% infill and at ~45mm/s print speed it takes less than 2 hours to print.

Fusion 360 model is included in case you want to alter for your needs.