Hmm, that's interesting because the 2363 I had must have dealt with the same situation and part of the big window was plexi. In that case, the bottom half of the window was a jalousie and the top half was solid/stationary. The stationary part was the plexi part, and it was starting to show some stress cracks along the bottom.
The window on that one was a Hehr, so I went to a local glass shop, Henderson Glass, and inquired about replacement glass. They advised it had to be tempered, and they needed the model number off the window itself. This required removing the entire window unit from the trailer to access the sticker on the back side of the window frame. They ordered the glass in and it went in like a glove.
In your case, you should have Kinro windows, but the process should be similar. You could also try calling Kinro to see if they can help about getting a replacement glass: Contact
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR