[quote name='crawdd']Where can I gret Season 4 disc 1 (And only disc 1, the rest of the dvds are fine.) Does anyone have it for sale or anything?[/QUOTE]
Honestly, the only chance you MIGHT have of finding it would be to try going to a video store. Occasionally, Blockbuster and Hollywood Video and the like sell their extra copies, and I've seen shows like Desperate Housewives sold off as individual discs before.
Other than that, you're probably screwed.
Moral of the story, as Leggo said, is to not buy used discs from eBay. If you can't look at it in person before buying it, it's not worth the risk.