You have to sign up for it, but Gendou's Anime Music (http://gendou.com/amusic/) has lots of mp3's for various anime. I looked and they do have KKM EP/OP.

Stop-Tazmo has direct downloads here : http://www.stoptazmo.com/d.gray-man/ You should be able to figure out where you left off.

Here is So Wa Reirei no Yukini Mai : http://s52.yousendit.com/d.aspx?id=2XVGVYZ86VD230TCEFCKBNVLG1

Hope that helps. :)