Yes, you can replace just the plexiglass if you are willing to disassemble the frame.
Remove from the trailer, remove weatherstrip, drill out rivets on closure part of frame, frame has 90 degree angle in the corners that you slide out of alum frame, remove old plexi and rubber cord, use old plexi for pattern and cut out new, reverse process.
I replaced mine with Lexan but now not sure if that was the best way to go, costs more and more impact resistant than plexi but not sure if it's as scratch resistant. I cut the Lexan with a jig saw and a fine blade.
Cost me $270 mainly because I had to ship full sheet, others have own ideas on this.
Good judgment comes from experience, and a lot of that comes from bad judgment.