Any inexpensive digital thermometer
with probe should do. For that matter combination hygrometers/thermometers
with probe are pretty close to the same price, so they're an option too.
https://www.amazon.com/s?k=digital+hygrometer+with+probe&ref=nb_sb_noss_1
Go through a few pages. You'll see quite a bit of difference in prices for basically the same units (and those packaged for reptiles are obscenely priced). IME, they're all pretty much the same, so it's worth picking up a multi-pak just in case.
Avoid analog/dial types; they are notoriously inaccurate.