I haven't been able to find the cubes anywhere for a reasonable price so I decided to go with the wire mesh panels from homebase which Wheekster told me about. I've made the main cage all I have to do is the base and I'm going to make them a small second level using tubs. Here's a picture of the cage so far: https://www.guineapigcages.com/photos/showphoto.php?photo=2647&password=&sort=1&cat=500&page=1