Print in ASA or ABS. 30% infill , no supports.
Activated carbon can be purchased in kilos on the Internet and in aquarist supply shops.
Edit- At your request , I have added a version with smaller mesh holes for the smaller 'Nevermore' carbonpellets.
This is a remix of the 'Sliding dessicant box' by Shrodix on thingiverse
The author marked this model as their own original creation.