The probability of finding one is low. If you do find one, the probability of finding it useful, is even lower. Save the effort. Motorhome manuals were (and still are) written to cover many different models. They tend to be very generic and not terribly useful. You might just as well get a manual for any current, gas or diesel motorhome, depending on which you have.
What will be helpful, are the specific manuals for the furnace, fridge, water heater, water pump, dook top, converter, awning, etc.
Retired electronics engineer. Avid paddler & birder.
2011 Silverado 2500HD, diesel, 4x4,crew cab, 8' bed
Palomino Puma 253FBS (27' 5er) & '94 19' Class B