I've re-shafted a few of the fluted aluminum handle ones. I bought new screwdriver shafts online. They are the long 5mm bits for power screwdrivers. The tip is hollow ground. The length inside the original is tapered. I cut off the new ones and used a drill on a sanding belt too get the taper. Removing the old one was simple heating the handle with a propane torch and pulling the shaft out. Installed the new one the same way, shrink fit.