There are lots of different kinds of convertible beds in molded fiberglass campers, but none that fold up into the wall, Murphy-style. They are more common in conventional toy haulers, I think.
Not sure what is your reason for asking about them… perhaps you are wanting to carry a motorcycle(s) with you…? Most fiberglass trailers are built for light weight
and have very limited cargo capacity. The Happier Camper HC1
does have a rear hatch and modular interior, but it would be limited to a very small dirt bike.
If you really want to carry motorcycles and have a molded fiberglass RV, your wife may have the best idea. Bigfoot
makes some nice fiberglass slide-in campers and you could pull a motorcycle trailer behind.