I recently replaced my rear window, it was not a difficult job. Mine was the original Lexan flat window. There were 2 significant cracks near the fuel filler, and several crazed and cracked areas around screw holes at the roll bar. They were much worse than yours. I did stop drill the cracks near the fuel filler until I got the new plexiglass window.
I ordered the plexiglass rear window from Vanís, and picked it up from Airplane Plastics in Tipp City Ohio where they are manufactured. I saved shipping and handling. I noticed that you are in Ohio, so that might work for you.
RV-9A, Under Construction
Xenia, OH 45385