There was a nice thread about the D-tool on the former site. Many solutions were detailed, but the one I liked the best was this: use a short piece of 1/4" plastic drip tube (yard watering stuff) slipped onto the end of a phillips screwdriver. The plastic will deform enough to go over the D shape and it's cheap at your local hardware store!
My idea was to use a small piece of brass or copper tubing, shaped (blacksmithed?) to the D-headed screw, and solder that brass piece onto a screwdriver shank.
