If you're just looking for standard tickets there's a link on this page. http://www.mlsnet.com/special/mlscup/2003/tickets.html
Patrick Bernal, the Club Quake Events Chairman was organizing a group purchase for Quakes fans. Not sure if he's ordered yet, but I'm sure there will be more interest (and possibly more group orders) now. Not only do you get seated with Quakes fans, but you get a couple bucks off the regular price. I'd send him a note: events@clubquake.org