I would have thought two types, basic one with welded on cab protector and the one with the extended wheel arches. ( What model do you have? )
There should be dozens of these tubs around the country as many fleet buyers ditch the tub and get trays fitted by the dealers. Then there are the set who do tray conversions on their up market models to go touring.
I'd say they figure there's more money in a quick cut and paste for them than spending time looking for one and paying freight.
My concern with the cut and paste would be the possible rust outbreak in future.
Don't let the b'strds get you down!!