I tried to buy the rear unit for our 1991 Scamp
16 from the Scamp parts store. They said the best way to get one is to stop by the Scamp factory because shipping is so expensive. The problem is they ship them out and they sometimes arrive with a little scratch and people return them. As a result they've reached the state where they have to over pack them.
As a result I made my own. It can be seen at Modifications/Preparing a 1991 Scamp.
The way I built mine requires putting no holes thru the fiberglass.