Digg, Facebook, Myspace, Prism and Twitter

Hey,

I am wondering if anyone knows where I can get a Digg, Facebook, Myspace, Prism and Twitter icons from. Preferably in PNG format. In the link you can see what I'm using now, but they don't look good, especially facebook and twitter.. I also need a Prism.PNG icon the same as the shortcut on the very right on the desktop.. I can't find anything close to it.

Thanks!