I bought my earbud/mic extremely cheap on Amazon. I also got just a mic, but when I plug it in, it cancels out the sound, and I can't hear the other person. Not sure if it's like that with all mics, or just the one I got.
Yes, best buy, radio shack, or online. But not all seem to work. I use my touch to make skype calls it works great even between 2 touches and free. You both have to be in a wifi hotspot though. Good luck