I'm working on a new project for fun at the moment. It's a little robot that wanders around collecting envinromental data and one particularly useful bit would be a pH reading of water. Judging from what I've seen these probes all have a very similar form factor roughly the size and shape of a magic marker. I'm not sure if this is partly due to their intended use by human operators or for some techincal reason but so far I haven't had much luck finding a miniaturized pH sensor that I could cram onto this little guy. I did find this one ebay example, not sure just how much I'd have to add to get a useful signal into a microcontroller but we're getting into the ballpark now. I also saw this article from 2016 but I haven't found a "for sale" option for a component like that. Also, they seem like a bit of a hassle with all the calibration and maintence- maybe not worth the effort but I'd be delighted to hear some ideas from anyone familiar.
BTW- as this is a technology demonstrator cost is a factor and accuracy isn't (particularly).