I happened across two other Ozempic cases, liked what I saw, and luckily read the comments before printing to discover that not all injector pens are the same size. I've attached a photograph to show the pen pocket with a steel scale: the pocket's dimensions are 160mm x 20mm. Each case half has a 10mm deep recess for the pocket.

Four 8mm diameter x 3mm thick magnets hold the case closed; the recesses for the magnets provide a very light interference fit without using adhesives.

The hinge uses 1.75mm filament as hinge pin; the hinge holes are sized to allow the filament to slide through with only a little force.