http://www.guineapigcages.com/
Yes that's a GP site, but they are the same type of cage, you can go up for rabbits though, people have 3-4 floors sometimes. In america they can get the grids really easily, and cheaply, here its harder, but someone I know has found out from B&Q that they are getting them in November (Argos used to have them but no more, they are made for storge rather than cages, but make great cages).
Another forum has lots of pictures of rabbit NIC cages, but I don't think I can post the link here?