This box has a large sliding lid that wedges in place on the back and sides, and accepts a standard padlock on the front. It is about as wide as I can make on my bambu print bed. It should fit on a Prusa XL, but not on a MK3 or MK4. I've included the CAD file if you want to scale it down for your needs.

I included a blank lid as well as one marked for medication.

Print everything upright, no supports. I used the extra draft setting, but increased wall loops to 5 and top and bottom layers to 4 for strength. I used my AMS to print the labels in color.