Go to Martins cages online and order one. They have the best cages. Make sure you get the wire coated and that there is enough room for 2 rats. Online somewhere is a cage calculator where you put in the dimensions and it tells you how many rats can fit in the cage. I forget the website for it. Also on this site:
http://www.goosemoose.com/index.php?..._smf&Itemid=61
people sell used cages and most are usually Martins. Good Luck!