Here is a picture of the cage and lid I made for the top of it:
http://www.cavycages.com/photos/showphoto.php?photo=1692&password=&sort=1&cat=500& page=1
It was extremely easy to make. I just measured the cage and then went to Home Depot and got the linen shelving and told them the measurements I had and that I want the lip to hang over on each end. They cut them for me and I just laid them on top of the cage and connected them together (I had a few since it was a large cage) with cable ties. The was the only work i really had to do was attaching the cable ties and buying the shelving.