If the forks are steel, you can drill a 6mm hole right in the center about 13mm up from the bottom of the steerer tube. I'd recommend marking the spot with a center punch first, and only attempting this if you have access to a drill press. A straight clean hole that is perfectly perpendicular to the steerer is necessary. Use an HSS bit and a jig if the fork won't lie perfectly flat on the table. Bit speed should be slow, and pressure should be firm. A little cutting fluid wouldn't hurt either.