Bobkat,
Get high temp silicone at an auto parts store, but I wouldn't put any on the Tel-Tru, no reason, it won't fall out and it's actually useful to be able to rotate it. I like to rotate it so my target temp is at 12:00 (straight up). It makes it easier to confirm it's at the correct temp from a distance. It's an old trick used in aircraft and race cars, turn the gauges so all the normal states are straight up, it makes it easy to see at a glance that everything is A-OK.