A company called Alan Smith Garages (UK) used to make/supply them along time ago. They could have even been alloy as opposed to the fibreglass ones and I have only ever seen them fitted to vehicles (eg. never seen one for sale).
The pic I posted earlier of the RRC with the trailer on was taken by me when I sold one of my old Rangies. I will see if I can track down that owner. His 2 door had quite a few fibreglass panels.

