There are several people on here that have cat enclosures and that have posted threads about them. Here are a couple of links you can check out. Some of these threads have links to other threads or sites with other ideas. I think that is a great idea actually. Hope you can figure out one that suits your needs.

link one

link two In the third post of that second link, are some others that I linked to before.

Check them out and let us know what you come up decide to do.