NavList:

Ridge White, you wrote:
"A very well equipped hobby shop might have square brass stock with a square opening. A search online for metal stock for modelers might turn something up. "

Or as someone suggested (Peter?), find some ordinary, round brass stock and crimp it in a vice to make the end square or at least elliptical in a way that will grip the square head. It doesn't take much.

And you added:
"We once hired a retired jeweler with a lathe and broaching tools to make copies of Plath wrenches, about 30 if I recall, and they finally sold out and the jeweler has passed away. I might look to have someone else do the same."

Instead of a retired jeweler, the requirement for 2017 might be a middle school student in need of a digital shop project. These tools are easy to set up as 3D designs. They're very simple shapes. Basic plastic copies can be turned out on hobbyist 3D printers as prototypes. These tools do not need to generate much torque normally, and plastic versions will do the job, at least for a while. A service bureau --there are many to choose from-- could then print multiples in hard metal if desired. They could be produced almost indistinguishable from the original tools. Of course, it would be easy to improve on the ergonomics of the standard tool. It would be nice to produce a pair of tools as a sellable product: one exactly like the original tool to satisfy the conservative viewpoint and one that works better ergonomically to satisfy rational efficiency (and the latter would eventually wean people off the old tools).

Frank Reed