Oliver, if you are looking on the small side and don't mind that it is plastic rather then aluminum. The largest Oliver might be about the bottom end of your size range.
Bigfoot does molded plastic trailers in the 25 foot range, but not finished like Airstreams.
In my mind, I you are thinking Aistream, the first step down is a molded shell plastic trailer. Anything built from slabs fastened at edges is another big step dowm, no matter how well constructed.
If you want an Airstream, and can afford it, the only people making them is Aistream. Their real competitors are long gone from the marketplace.
