antique shops/furniture stores
Our '57 Overlander came with a fold-down back, free-standing couch. I'll bet that armed with your trusty tape-measure you can find something in a furniture store or antique shop that would suit your budget, taste, and size requirements.
Here's a photo of the Overlander's couch, unretouched, unrestored and untouched by human hands for years (including dust rags, vacuum cleaners, and any other cleaning implements...)
havin' to fix my broken Airstreams since 1987...
AIR 2053 Current: 2004 Airstream Interstate "B-Van" T1N DODGE Sprinter
Former Airstreams: 1953 Flying Cloud, 1957 Overlander, 1961 Bambi, 1970 Safari Special, 1978 Argosy Minuet, 1985 325 Moho, 1994 Limited 34' Two-door, 1994 B190 "B-Van"