Special thanks to Xerxes and Belboz for helping.
Interscrew seems to be the best search term, but I am still struggling.
I have been moved to actually measure the dimensions of the thing I'm looking for, and it turns out to have a shaft diameter of 8mm (5/16"?) and a length of 54mm. That's significantly bigger than I guessed earlier and rules out the M4 sleeve and bolt.. Sorry to muck you about.
Interscrew seems to be the best search term, but I am still struggling.
I have been moved to actually measure the dimensions of the thing I'm looking for, and it turns out to have a shaft diameter of 8mm (5/16"?) and a length of 54mm. That's significantly bigger than I guessed earlier and rules out the M4 sleeve and bolt.. Sorry to muck you about.