I'm sure the windows can be replaced individually. We replaced a couple stationary windows last year. We first tried a couple dealers and the factory before going to Atwood Mobile products. All the dealers and the factory wanted to sell the complete window assembly rather than replacement parts.
Your best bet is to go to the Winnebago site and get the part number from the Winnebago site.
Click “Resources” on the top of the page
Click “Manuals & Diagrams” at the bottom of the page
Click “Parts Catalog”
Click the model year for your coach
Click the model number for your coach
Open “Windows and Vents Group
Download a coach specific parts list by coach serial number
Click on the Blue “Serial Parts List” button
Click your coaches model year
Enter your coaches five (5) digit serial number.
The first number shown will be the Winnebago number. The second number shown is Atwood’s part number.
Once you have the part numbers give Atwood Mobile Products a call.
They supply all the original windows and will be happy to sell you replacement parts. A couple words of caution. First make sure you have the correct part number. There are 2 diagrams for windows. One is for the single pane windows the other is for dual pane windows. Secondly call the 800 number early in the day. The woman who takes customer orders and ships them out works from 5:30 AM to 2:30 PM. I believe the switchboard doesn't open until 8:00 AM. They were very friendly and helpful. You'll be surprised how much less the parts cost when you deal directly with Atwood rather than going through a dealer or glass company