Summary

This uses sock-length nylons to make refillable desiccant bags for keeping filament dry. It won't spill and can be crammed into any available space. The nylon mesh doesn't restrict air flow compared to solid cases with openings. The funnel screws into the opening and makes filling a breeze. It empties easily for drying the desiccant. I use crystal kitty litter which is very cheap and works as well for me as the official stuff. (That's unused kitty litter. Used litter would be even cheaper, but...)

If you make one, 10% infill works fine. The thread clearance should be ample. If it is too loose, an o-ring on the plug should solve the problem. Note you only need to print one funnel.

You need 2 cable ties 12 inch (300 mm) long and sheer nylon hosiery. Ankle length is probably best.
Stretch the nylon completely over the top piece and fasten with a cable tie. Then fold the nylon back and fasten with the second tie below the first one. See the last two pictures. Fill with desiccant and go!

The first design had a hollow top. As the first one was printing I realized that would make emptying harder. I included it here but I would use the solid version.

This was designed in onshape. If you want to modify it, it is available at:
https://cad.onshape.com/documents/058e24f39b8eecc586904578/w/488107b50e4678ac5c93bc43/e/fb102c703e6dd2e1e17e0bac
That includes a circular design as well as this ellipsoid version.

The reason for all the colors is that this is a functional, not decorative, part and I was using up a lot of filament dregs.