Off the (online) shelf I know of this.
http://www.leaderbikestore.com/pd-leader-trick.cfm

It's actually 30mm, which is 2mm more than your current fork, which will make your bike steer slightly quicker

There's a lugged steel one that others have recommended in the past, but I can't remember where to find it, or what it's called, right now. Or you can shop around for a fork from another track frame: Bianchi Pista, Felt T1, Trek T1, etc...