You might try the ReUseIt Store. (Habitat for Humanity program) for a few doors and some hinges - hinge the doors together like a screen - secure to the wall with anchored eyelet screws at the top and bottom of the wall and the hooks at the top and bottom of the screen.
The ReUseIt Store in our area often carries the office area dividers that Ben mentions. If a screen idea isn't a go, how about a bookcase? Try Amity, Salvation Army Store, GoodWill. Look for a bookcase or two so that you could divide the space and create some extra space at the same time. Good luck