Britt,

I have no idea where to get these window/walls in the US but we rented a home in New Zealand for our honeymoon and all the windows in the home were of the kind you're looking for. The window walls were awesome! The link has some pictures. Hope its helpful.

Here is a link that might be useful: New Zealand window walls

WeatherShield or Marvin could probably build something like that through their custom services.

You might google accordian doors or try this website:
http://www.nanawall.com/

I know these are doors not windows, but maybe they can do custom sizes?

Here are some more bi-fold door manufacturers you could check out:
1) http://foldingslidingdoors.us/index.htm
2)La Cantina
3) Lanai Doors
4) Tostem America