Beaver Coach Sales in Bend bought a few trailer loads of parts when Monaco abandon the business. They have a lot of things in stock and a well managed parts department.
Another source is Northwest RV Supply in Eugene. For years they acquired surplus parts from the motorhome manufacturers that were in the Eugene/Coburg/Harrisburg area. When I was there a year or so ago, they had enough boxes and creates stacked high that were yet to be unpacked and cataloged.
The current version of Monaco has a service and parts facility in Coburg, OR.