Thanks for all the replies, I thought it would be easier, BUT one big revelation. I stumbled across the solution on accident when fixing my DIRECTV receiver. Turns out the nut fits an F-type connector. Connectors mate using a 3⁄8 in-32 unified extra fine (UNEF) thread
MIKE—HK / Infinity met my expectation of a low level of service and had no clue. Apparently it’s not a ‘stock’ post like you would think, turns out NONE of the 13 other speaker nuts I tried fit. I tried some off my power amps, subs, and other speakers.
SFARI—I tried that thinking it would certainly be one standard but it’s not. Turns out it’s the extra fine connector which is not readily available.
Thanks for all the help, now I just need to find the right nut to do the job.