Good find, Will, looks interesting. The only detail I could find [ https://vekotinverstas.fi/bxl-aqburk/ ] was a bit short on internal pix - did you find any more? They appear to use snorkel-type arrangement for sampling and I think this is the way to go. I have some ideas for mounting the components and hope to try them in the next few days…
This is the person who designed the custom boards. Their housing isn’t the same as the Finnish team, but another option (particularly with the cutom circuit board)
Note that some of the citation circuit boards support the D1-mini Wifi board - the pro version of that can take an external antenna & the there’s the LoRa version the Finnish team are using.
The 3d files are there in various formats.
I did start looking for flexible tubing options - according to the pro sensor people we should only use anti-static tube to prevent particles clinging to the sides. 20bar airline (6mm inner diameter) is a bit overkill, but it is cheap: