Unfortunately I haven't found anything like these sold retail in stores by themselves. However, I did find some cheap bath salts packaged in them in one instance, glitter in another, beads in yet another, and bubble blowing liquid that had a lanyard that attached to the cap as well, so I bit the bullet, bought a few, dumped the contents, and cleaned them up. Most of the time I ended up paying around $1.00 to $2.00 for these, so it can get expensive depending on how many you need and if you experiment with different sizes.
I have seen them on ebay from time to time. If you do a search there for "plastic tubes" then some will generally show up for crafts storage, or in some instances as labware, though the latter are essentially plastic test tubes with caps.
When I started playing paintball about 15 years ago or so, paintballs came in tubes of 10 with a plastic cap. I can't think of how many of those I threw away back in the day. LOL
I do have a pack of ten left, but I keep them with my old Splatmaster as nostalgic pieces and part of the display of markers I've owned over the years... OK... They're all packed in a box, but it sounds better to say that they're displayed. HAHAHA
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"Learn survival skills when your life doesn't depend on it."