You'll need to be able to get to the probe to re-calibrate it with buffer solution every month or so. Just keep the Diod in the water and you can submerge it, I believe, tho I don't own one. Near the intake is fine is my guess.
You can get some suction cups (four in a pack) from Big Als for about $4.00, maybe less. Thats about what I paid for some Rena XP3 suction cups for replacements on a few that flattened out over time. Seems kinda spendy for 4 little cups, but they're quality Rena rubber, I suppose.