I just bought a new packet of grommets today, TheShaun. $2.49 plus tax at Ace.
The online source that D-man found is much cheaper, though. If you decide to try them, make sure you get the 1/2" ones -- 1/4" doesn't work unless you have a very dense string pattern.
I use #64 rubberbands in some of my racquets and hole grommets in others. The RBs dry out faster, but both work very well.