1930 Model A engine running hot

[KCW]

I’ve got a 1930 Model A. When I got it about 8 years ago the previous owner had installed a temperature gauge. It’s underneath the steering column. The engine has been running hot and a friend of mine suggested that perhaps the gauge itself is bad. I was thinking of replacing it. We’ve tried everything else. Attached are a few photos. One is of the gauge itself and another is where it inserts in the engine. Not really sure how it work. Does anyone know where I might get a similar one to swap it out and where? I can’t imagine it’s that difficult to install. Thank you everyone!!!

PS. Drove for ten minutes the other day and the engine read 210degF. Spark was timed appropriately.