Do what I did . Replace the junk that came with the unit and put in a River Country therm
Unless you have a new unit with that silver dollar size flat thermometer . Then a piece of flashing and some high temp silicon is in order
Well so yes i have the style with the great big monster hole with the snap ring type thermometer. My idea was to get a piece of metal and then with some metal working and luck get an indentation about the same size as the hole then place it in from the underside to really help then find some decorate thing to cover the ugliness that will become.
Here is a thought .. Did this on my brinkman
Vertical .. Same therm .. Take it out break the glass rip the guts out . Now get a good therm and drill a hole in the center for a real therm
Reinstall with the snap ring and new therm
And now you have a perfect fit with no leaks