Bought branded products which are essentially a silicon sock for storing a key, but I found they broke/tore after minor use. A problem with keys is they punch through whatever you're wearing (e.g. wetsuit) and tear a hole in your expensive gear.
I made this TPU cover for a larger car key with no electronics/waterproof electronics. Push the key inside, strap it in (or don't) with a shoelace/string and put it around your neck. In my case it gets tucked under a wetsuit right at the zipper on the chest in the arm pit. It won't move, you won't feel it, and the key won't stab you by accident on a Wipeout. If the shoelace breaks the TPU case will happily stay inside your wetsuit anyway. Cheaper than having a car stolen because the lock on your car was cut.
Good luck getting the key out with your cold hands, it does not come out. If you want a thinner, or longer/shorter key holder let me know. It should not be hard to modify.
Printing:
Print slow on any FDM printer using TPU with a layer height of 0.2 mm and a 0.4 mm nozzle. Use supports (grid) for the tabbed holes on the sides. 10% gyroid infill. An SV07 prints happily at 25 mm/s with supports and small perimeters at 15 mm/s. Temp at 235 *C, and bed at 60 *C. Print the first layer at 5 mm/s as TPU has trouble sticking and you'll need the good surface for the small print.
The author marked this model as their own original creation.