This is a very simple design I improvised before a trip to protect the filters (non-variable ND filter and mist filter) before at trip.
It consists of 2 identical parts and the filters are inside.
I printed this in PLA and the filters fit tightly inside so that they don't fall off (your experience may vary from printer to printer).
Then I used a small piece of velcro to keep it closed. The 3D print has a small groove for the velcro.
I did this in 15 minutes and is probably not refined enough, but perhaps someone finds it useful.
The author marked this model as their own original creation.