First, you are asking for serious trouble with any kind of tape in the enclosure! It's not worth the danger to the snake.

You have a couple options. You can secure the probe above the UTH with aquarium grade silicone. This will make it difficult for cleaning.

Your best bet is to attach the probe to the under side of the UTH on the outside of the tank. Use aluminum tape to secure it directly onto the bottom of UTH. You will need to prop up your tank a little for clearance so it's not resting directly on the probe.