I was just thinking, I have some really large diameter heater type rubber hose, I think 2 inch.
I could cut off a 4 inch long piece.
on one end, cut a 1 inch hole in bottom of the hose and slit it to the hose end from hole to hose end only on one side.
pull off the positive cable, slip on the hose
tighten up cable and slide rubber hose back over the terminal
the cut hole accommodates the battery terminal and the slit part is forward of that sort of locking it in place and covers the whole terminal and cable.
So the cover simply needs some holes drilled in the top to keep hydrogen gas from accumulating. I think I had made a cover, I might just do both. I recall
it fit on top of my tray and was strong enough I could stand on it.