I had it done on a Soma track fork from Neal a while back. Bernie cuts the steerer off, inserts a plug and then welds a threadable-thickness steerer on top. $50.00 was what he charged me, return shipping included. When I got mine back, it was VERY difficult to even see where he'd done the welding. Great job, and I have no doubts about its strength. Dokushoka has a bike with the same modification- that's where I got the idea while searching for a for with minimal rake.

The downside, if you can call it that, is that the plug keeps you from using a long-quilled stem like the kind you'd get from Rivendell, but no one here seems to use those stems anyhow. It may not work if your frame size is really small (short head tube).

In other news, I have an as new chrome straight-bladed uncut 1" threadless fork, but it's a road fork, drilled for a brake. PM me if you're interested in a purchase or trade.