Yes, Craigslist has windows all the time, however you might not feel like waiting for whatever length of time it takes to get 8 windows, all of the same style, and of the right sizes. Why not make your own. That's what I did.
We have a Habit for Humanity 'Restore' in our town. I've not been there, but have a friend who tells me they have wonderful stuff for great prices. If you have something like that where you are, you might check it out.
I happened to luck out. I had to go Syracuse(30 miles away) for some items for my camera. As I drove through one suburbs, there were piles and piles of yard waste and other non-typical trash. I think it was like a cleanup day. I drove slow and pilfered a nice window out of one of the piles...
They're around, you just have to look sometimes. Maybe even throw up an add or two around town. When people know you want something like that, they often come in hordes!