Roger, I replied to your posts in another thread, then came here and saw more info from you on what you're looking to do. Not sure if these would be of interest to you, but I'll mention it:
KZ Recreational Vehicles: Sportsmen® 16FKTH
It's a stick built travel trailer (FG heretic hunters, don't shoot me!) with a ramp rear, and just 17' long overall.
Or try this:
Quicksilver All Aluminum Ultra Light Campers, Ultralight Campers, Lightweight Campers, Ultra-Lightweight Campers
Livin Lite makes aluminum framed trailers with rear ramp door.
Since Lil Snoozy
plans to also offer "Lil Hauly" cargo trailers, I bet they will be able to offer a ramp door as well.