My boyfriend bought plexiglass and cut, heat, then bent it, to make a passenger window for our 1988 Classic Airstream Moho. Finding one was difficult to impossible and far too expensive, ($750 from the guy who did and then didn't have it). My Chris did an excellent job, you cannot tell it is different from the other windows except close up.
I just found the photos that show the process, 27 of them, so I don't think I will post. I will post the last one so you can see how it looks.
Your window will require more bending than this, if you haven't done anything like it before, have a professional do it for you.