Ah, I see.
Look for something with a NIST rating for the best in accuracy.

Also, as you know, these reptiles use large mass (the ground) to keep the egg temps constant.

In captivity in a small incubator, even a great temperature controller and heating system cannot necessarily maintain to 1/10 of a degree unless that air temp in the room stays constant or the incubator is very well insulated.

Those thermometers they sell at Radio Shack and other places for $20 or so will never have the accuracy you look for.
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Mark