What’s a good accurate room thermometer to calibrate my zwave temp sensors against?

Looking for a room thermometer that will measure temp and humidity so I can calibrate my various zwave multi sensors against. I’m 99% sure they are a few degrees off so I would like to check them.

I bought two of these Thermopro ones from Amazon which has like 49,000 reviews but they definitely are not accurate. They are several degrees off and even if I compare them to each other they report different temp and humidity :man_facepalming:

I’m frankly surprised this isn’t easy to find. So many of them on Amazon, including the one I bought, are criticized in their reviews by customers who actually try to measure their accuracy and they don’t perform well.

Given you all are freaks like me with home automation I’m certain more than a few of you have solved this for yourself. Any recommendations?

Maybe a little pricy, but come with calibration certificates. I used them for incubator monitoring.