I have a couple of Sheaffer Lady type pens and somehow managed to get the nib unit out of one of them by using a small international sized cartridge.
Inside the section there is a screw threaded nut below the cartridge piercer that has to be unscrewed in order to remove the nib and feed unit.

Now it's out I know it needs a 4mm hex key or a T25 torx key, but hex keys don't come with holes in them that would work with the piercer. I've seen some torx keys that may or may not have "holes" in the "long arm" and have already bought a set that had to be returned because the holes either aren't there at all, or aren't deep enough because they are only "dimples."

Does anyone know where to get a hex or torx key that's hollow and long enough for a section or maybe even a cap?
(I'm also thinking of attempting to unscrew the torx screw in a Montblanc Boheme cap)

I don't have a pillar drill so buying a random hex or torx key and drilling a hole through it would entail holding the drill by hand and fixing the key into a vice. Not easy to control drilling a strong 4mm key.

Pentooling don't have any tools like this. Sheaffer must have done at some point. So who uses what and where did it come from?