Trailer: Scamp 16' side dinette, Airstream Safari 19'
Maybe you could draw your own plan by looking under the trailer and taking dimensions? Most of these eggs are pretty basic and exposed to view.
If you are planning to build your own frame, you could pull the body off first and then copy the frame.
Pulling the body would seem to be the hard part. There are some posts on this site about swaps.
You may be able to tow the frame to a trailer/chassis builder to have it duplicated and then tow it back home to mount the body.