An alternate for one piece carpets would be the 2' x 2' carpet squares used
in large computer rooms, with raised floors. The carpet squares or tiles are
very heavyweight with rubber backing and tightly woven fibers. They can be
cut from the back with a straightedge and sharp utility knife. When in
place, the joints are invisible and the individual squares can be removed
for cleaning.
I covered the existing vinyl floor in my '90 Westy as well as the rear deck
underneath the matress.
I can't tell you where I got them other than that I used to work in a large
computer room and there were a lot of leftovers. You might try an office
supply house or commercial carpet outlet.

Jerry