Have you contacted
NuWa?
They might have an old one laying about.
That being said, most manufacturers "manuals" are generic and not worth much. All the usually have is generic RV information. Nothing on say where the wires or plumbing is.
Also nothing on the sub-systems, ie water-heater, furnace, refer, etc.
To get those you need to go the that sub-systems web-site and see if they have a PDF for that model.
Yet another option is the RV Repair and Maintenance Manual by Bob Livingston. Actually that book is a good idea anyway.