Any luck finding a Stahlwille Part Number? I'd like to find a 1/4 x 3/8 or a 3/8 x 3/8" as well.
there you go. Find a 3/8 piece; mill the sides down and pin it.Still not what we're looking for, but on the subject, here's a Wright Twin Flex Handle 1/4. P/N 4440. http://www.toolup.com/wright-tool_4440_twin-flex-handle-15-14.aspx
Looks like Stahlwille has a loooongstanding patent history on it.