Help Danger Room Discs

I know I'm a total jackass in not being able to figure this out, but when does Beast/Forge start selling Danger Room Discs. I have all of them that you can find in the game in the first act right now. I don't want to move on until I'm positive that he sells them later. The walkthroughs all say that Beast/Forge sell them. But they are not being sold in my game right now. If it matters, I'm playing on Gamecube. Any help would be appreciated.
Thanks.