I'm looking for the same thing, myself! I've been looking up and down the web for one. Well, finding any fork drilled for a brake is easy. Trying to find one with track geometry (35mm of rake or less), for an integrated headset, has been killer. It's proving damn near impossible.

I'm unsure if you're looking to preserve the geometry of your pista, or not. But in my searches I have come up with a few track forks, drilled for a brake. However, finding one for SALE has yet to bear fruit.

Here are the ones I have found

http://www.planet-x-bikes.com/track/...sition=256:256
But they are not offering the drilled one for sale. The one pictured below, appears to not be drilled.

http://www.feltbicycles.com/index.ph...tk2frameset_07
But this fork is part of a complete frame(set)

http://www.spiuk.com/home/productos-...ing.asp?id=330
The page makes no reference of this nike's fork being drilled for a brake. Having seen this bike on Fixed Gear Gallery's Interbike photos. A hole for a brake is clearly visible. http://www.fixedgeargallery.com/repo...y2/77x1000.jpg Also part of a complete frame...

I'm not sure if that was any help. But I'd be very interested to know if you find a fork, with track geometry. I'm hoping the Sages of the forum will be able to help, as I am looking for the same thing... maybe.