I look after a D3 here for our hockey team. The double pane windows do get fogged up on a regular basis. I have bought some from Crystal Glass in Calgary for IIRC $300 and change. They take them apart and rebuild them. They supply several local bus companies. So you should ask bus charter companies around your area where they get theirs. Also last year, someone nearby was converting a C3, and gave me 5 or 6 windows. That was great. I still have 3, but am keeping them.