When I went looking there was NObody in the Bay Area who would add threads to a steel steerer. I ended up shipping it all the way to NY State! The job there was performed beautifully and without drama, I had to sand off all chrome in the affected area with emery cloth...good thing Emeryville is nearby!
The guy in NY who did it cut the threads with a lathe, I think that's the only proper way to do it, chrome or no chrome, since using a die can be dicey.