During my war with small space for printers, I found place to store all 3 plates for PrusaXL. It is on fencewall, so I made simple model for keep all plates on one place. Of course, it can be mounted on wall, MDF or any vertical surface. 

I did't test it, but as this 2 parts can be adjusted in width, it can probably holds any square plates, such as i3MK3, CoreOne, etc. 

Holes has diamemeter 5,5 mm. If you need adaptations, you can find Fusion360 file here as well. 

Print it from whatever you think. I made mine from CPE-HG100, but for sure PLA will work too. Supports not needed, I recommend 3 perimeters and about 10% - 15% infill.

If you print this thing, I will be happy to see your make in "Post a make".