Put the switch before the transformer (unless the transformer is being used as the fluorescent ballast).

It seems like the transformer is the ballast.

just disconnect and isolate all the wires inside

Hang it from a wire and take a piece of round plastic and put a whole in the middle and cut a line from the hole to the outside, and then attach it to the wire/rope and overlap the piece of plastic and glue or tape it so it looks like a small second roof over the bug zapper, I do this to stop the rodents getting to the bird feeder and the bottom of a plastic ice cream bucket works great, it feels kinda slick and they slide down and hit the ground so it might work for lizards..