Results vary. Grommets (actually, piece of rubber band) worked for me since the sound was mostly from the drive vibration; YMMV. As for cork, it's the same thing. LegendNH recently did a very good ...

I got the ones I have from 2cooltek.com ages ago.. Ian's closed his shop now, but I imagine it wouldnt be too hard to get them at other online mod shops. The ones sold for fans would be much too large ...