It may be a long shot but you might look or call one of the several RV salvage yards around.
The older,2005 or so Majestic,A Former Cruise America Rental,had a slide out generator according to a member here.
gotsmart wrote:
I should add that the 28R has surprised several RV technicians for being a rental with a slide-out generator. I open the generator cover door and can pull the Onan Microquiet 4000 right out.
These were made by Four Winds so the non commercial ones may have them too,you might be able to modify one for your use.