Sensor hole plugs?

So after a few seasons of unreliable sensors I decided to put in some Hoist sensors along with a internal tank sprayer (quicky rinse). I had issues trying to remove the first old sensor, so I decided just to drill new holes and move the wiring. I've got two done, but having some difficulty getting the nuts off the old sensors as the whole thing spins.

I guess my question is, do they make plugs of any sort to replace old sensor holes? I plan to leave the old sensors in, but if I have to yank out the old one, I'd like to be able to plug the hole obviously lol.