I’ve done a modification to add an Optronics 7-Way trailer harness plug protector.
Here’s the link to the part I used from e-trailer.(Including shipping and tax < $10
https://www.etrailer.com/Trailer-Plug-Covers/Optronics/ACP7B.html
7 Way Plug Protector - by Optronics
And here’s where I mounted it…on the back of my Tongue Box.
I used stainless #10 bolts to mount the unit.
It could be mounted with zip ties to the bottom of the tongue as well if you don’t want to drill holes.
The cover is a semi rigid type of rubber material but with enough flex to make it easy to insert or remove with one hand.
In any case, I switched to this after my original “rubber cover” leaked.