I have a small wireless indoor/outdoor thermometer, the Acu-rite 00782. I'm pretty sure you can get them at Walmart for $10 or $15. The batteries in mine lasted all through winter and are still working.
You could consider using your camco unmodified for inside use only. Then
buy the Acurite 00782 ( not much more cost than connectors and wire to extend the camco) and use for reading from outside the TM.
Mounting the display unit on the inside of a front shell window so as to view from outside would afford some protection - it would be between the shells when the TM is closed up. There are several ways to hold the display unit to the inside of a window. I found that the display fits in between a window and its screen - the screen holds it in place. Alternatively you could glue it to the inside of a window (auto rear-view mirror glue) or velcro it to the back of a curtain, etc., etc.
Paul
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