Romahome are still in production with the first of these models - a minimal two-berth model:
They even now make a smaller one-berth model, whose 1400cc diesel does 63mpg(UK) - well over 50mpg(US). But this is just a converted van, not the molded fiberglass of the one above.
But even these are monsters compared to the stick-built Bambi, a demountable that went on a 1000cc Suzuki 'pick-up' micro-truck:
12'2" long, 5'8" wide, 8'2" high with standing headroom at the back. It could drive into headwinds at speeds well over 30mph.....