This is kind of late, but I'm going through the same thing now and thought it might help a more recent inquiry.
I just called Forest River Customer Service at 574-206-7600 and was transferred to Kathy Wing, Sunseeker Parts Department in my area (CA/AZ), and she said I could order it through her.
It's called Window Glazing and for my motor home (2006 Sunseeker 2200 with a rear kitchen) the kitchen window glazing is part number 20X24242A. I would call to order and they can confirm your part number.
(PS - my "cabin" is a 2007, but the Ford is a 2006, so it sold and is registered as a 2006. When I ordered a new compartment door, they couldn't find my rig listed until they figured out it was built in 2007. FYI)