Some Impact toy hauler travel trailers (not fifth wheels) have a Onan 5500 option available. There is one online at an RV dealership in MO. https://www.rvtrader.com/listing/201...216-5000457802
Typical price for that model looks to be around $38-44K. This one is listed at $54K, so...... Anyway, yes, there are some available, but few and far between. You'll probably find it's easier to search for a floorplan that works and do a "custom install" if a generator is an absolute necessity. Otherwise, a portable generator and settle for running one A/C ??? Good Luck in your search.