Hope the person who posted this picture of their car on the net doesn't mind me re-using it, but this looked like a simple home made solution for you.
He descibed it as a goretex type material, breathable, water proof etc, and it's elasticated front and rear with velcro securing it to the edges of the chassis.
I think this looks quite neat, but makesure it doesn't come into contact with hot things or moving things
