Apparently the
Quantum was a short-lived fifth wheel from the '80s.
Bigfoot continued into the early '90s. Scamp's fifth wheel is currently out of production (as are all Scamps until their factory is rebuilt). Scamp's "fifth wheel" is actually a goosneck connector using a standard coupler and two-inch ball on a "fifth-wheel style" bed-mount apparatus.
I suspect that while popular, the fifth wheel market is more limited than the standard trailer market.
Roger