I have a 1994 LY and have found replacement parts at PPLmoterhomes.com; replaced fan motor, switches etc. Airstream is best source for non-specific manufacturer parts such as door latch I replaced this spring. I have had great success contacting makers of various systems directly. (Fantastic Vent sent me a new fan mount and motor at no charge to replace broken mount) Other than that, Tom Raper Rv in Richmond Indiana has a huge parts department.
Hope this helps