I picked this sensor somewhat randomly on Aliexpress and it seems to work well (with calibration on both, tracks closely to my commercial Nutra-Dip Trimeter).

For hydroponics (where 0.1 pH is plenty of precision and pH range should be inside 5-8), I was quite happy with the $14 version below.

https://www.aliexpress.com/item/32957428276.html?spm=a2g0s.9...