that those things don't have a built in UV sterilizing light.

Where do you get your distilled water? Have you considered making your own? About a hundred bucks will get you a decent electric still. There was a post on local social media with someone with a CPAP who could not find distilled water in the store due to the supply issues. Might be a good idea. Microwaving the water might help?

It might be interesting to grow a culture? Is there a local lab that might do that?

Given where you live, I would suppose the moist air is full of all kinds of interesting bacteria / fungus.

Update: Microbial life at extremely low nutrient levels https://pubmed.ncbi.nlm.nih.gov/11537832/