If its a fireglass shoew cubicle the only real option I can think of is to back it with some pieces of wood or some similar hard material (slide a couple of pieces if neccessary thru the hole and then back so they completey cover it if needed and pin or glue them to the wall to stop them dropping) then use car body filler to fill the hole level. After that if its white, you might get away with sanding and painting it. If its coloured then maybe you will need to disguise it with a stick on soap dish or something.
Pete K, January 2006