Spice/salt shaker designed to be taken backpacking. I needed something that was compact, wouldn't spill when packed away, wouldn't have additional caps to lose, and could be operated with one hand. Hopefully this will work, I haven't had a chance to try it yet.
I used NinjaFlex for the plug (if you use other materials, you'll probably need to adjust the size) and put a 6mm diameter x 4mm height cylindrical magnet inside This lets me attach two shakers together at the base or stick them on the fridge, fuel canister, etc, but it's not necessary.
There are several versions of the exterior tube, the number is the microns gap between the inside and outside parts. You may need to try multiple versions to get a good fit, especially if you're using different materials for the inside and outside.