Have you ever wanted to have a different drivers window? If so, then here's your opportunity to put in what you want. Something to consider.
I would think someone inserted that glass in there originally, so why can't someone do it again. I'm betting a local glass shop could help tell you how, or an auto-glass shop could actually do it.
I know all our school district just take the buses to the local Speedy auto-glass.
Here's a link to Lippert (hate this company, but I'll refer it for another skoolie) who has windows for school buses.
Hope this helps.