Adaptor plate for outlets

The outlet and switch boxes in my basement were installed with 1/2" drywall in mind. However, I used 1/4" pegboard. The switches and outlets are rock solid, but there is an irritating 1/4" gap between all the plates and pegboard. Is there a product to fill the gap? Obviously box and outlet extenders are not the answer. Must be some sort of thicker plate, or dummy plate.