Yeah, ebay or something is a good bet. However, I'd ditch the little button, and replace them with a set that actually sound good. I use a set of Shure In Ear's, and they are fantastic.
I would recommend buying a better set of earphones/headphones but to tell you the truth, the quality that the iPods play back at are total crap and it would be a waste of money.
I'm with Alex, and disagree with Evan. I think if you've ripped them OK, they'll sound good. I use a set of Etyomotics on my phone, and it sounds more than acceptable. I doesn't sound as good as my home stereo, but considering the the trade off between quality and portability, they're fantastic.
Quite a few manufacturers are now doing 3rd party ear & mic sets.