Colin: I've wondered that, too and scored about 20 tiny toothpaste tubes from stays in Chinese hotels but I hadn't thought about repurposing them for other gooey stuff.
For antibiotic ointments, hydrocortisone or the more potent flouridated versions, mini sunscreens, etc, I use the professional medical samples the drug companies give to MDs (so they start the patient on the free stuff and potentially the patient continues with the brand-name stuff).
I ask a Derm guy for skin stuff, internists for oral antibotics, urologists for Viagra, etc. The creams are great because of the small tubes. The pills tend to come in over-sized packaging that needs to be consolidated.
Untested brainstorming here: Could you heat-seal soda straws? Most are HDPE, so you should be able to if you get the temp right. Then squirt the goo in* and either heat seal the other end or plug it with a dab of caulk. Not so good for multiple uses, but the materials are almost free and likely already around the house.
Please label whatever you store like this. We're never at our cleverest in a crisis nor at altitude!
*For squirting the goo in, you MIGHT be able to be use a hypodermic needle, but most have very small needles and you're talking about some pretty viscous stuff. The grocery store has "flavor injectors" that are over-sized needles on a clear syringe. I keep a number around the house for various undisclosed reasons.