I don’t travel much anymore but, I think this may be helpful for those that do. These are prescription bottle. I use them currently for storage of brushes that I’m not using. You may want to drill a small hole in the top for moisture to escape.
For those of us who love observing with a telescope, it's not uncommon to put an eyepiece in a pocket or stick one in an accessory pouch. But, not every telescope eyepiece comes with a plastic case. Zippered plastic bags and the original cardboard box is fine for awhile, but they wear out and...
Of course there are also tubes specifically designed for brushes. Epsilon, Mühle and Simpson market them under their brand name. I have one that was sold by Mühle.