Did it arrive in that way, or over time? If you can find an acrylic place you may be able to get a custom clear one made.
T-Cut is your solution. I had the same issue with a corsair 600T case. It was all blurry and was not happy. Some one on here said T-Cut and I thought ....What...The car scratch remover? Yes....that's the stuff. I buffed T-Cut on the case window leave it on for 10 mins, then buff it off and it was a miracle. It was clear as day.
Just go to halfords and buy the regular T-Cut. It's a red tube. I'm telling you now you'll thank me later![]()