I use this small (2cm diameter) desiccant container to replace the desiccant bags provided by the filament supplier. You never know how much water is already in there.

The model includes a fitting funnel for filling the container.

The holes in the container are only 1.25mm wide, so should fit most desiccant pebbles.

No supports are needed, though the funnel may need a brim if adhesion is low.
Apply some fuzzy skin to the cap outer walls for better grip.

I printed in (transparent) PLA and 0.15mm layer height (0.2mm works too). For better tolerances I used -0.05mm of XY compensation. See 3MF file for Prusa Slicer print settings.