I have
this one
On ebay they list 10$ less, like 90$.
Non lab grade but kitchen alchemist friendly alternative.
I like the replaceable electrode, pen's usually do not.
Long chord and slim electrode to hang in the pot while having 1 hand free for stirring and other hand for adding acid/base.
Very stable calibration, after months the 7.00 went to 6.90 only, I store the electrode in calibration fluid 7.00 (official electrode store liquid is not cheap and for now I can't imagine doing better)
I think the 9 volt block battery supply does a good job, my previous pen had button batteries that tend to sink voltage after initial startup, so had to wait for stability each time before a reading was done. Not with this one, fast stable working readily after after ON.
I've access to plenty of lab calibration fluids and could see the little white provided bottles failing to concernable accuracy after a while they've been opened/stored.
It's a glass electrode inside a plastic protecting tube that saves the day on a bumpy occasion.