I made one by cutting a slot in a screwdriver using a Dremel Tool with a cutting tool. The cutting tool also works well for reslotting screw heads that have been messed up by ordinary screwdrivers. Gunsmith\u2019s screwdrivers are the best for all slotted screws because the sides are ground parallel to fit the slots unlike most screwdrivers. If you get a set you can usually find the width for a snug fit in the slot preventing damage. Browenells Inc is one source.
George Jones Dallas, TX USA