PVC Probe Fitting Question

[Etaloche]

Fellow member was nice enough to give me an old calcium reactor they had lying around. The pump housing was broken so I have to redo the plumbing for it. While I'm doing the plumbing I wanted to add in a pH probe port since it doesn't come with one. I've been to corix and J&L and neither could tell me what fitting would work as a probe port. I only know it's some sort of compression fitting. Anyone here have a clue as to what they are called and where I could get some?