I've sent out emails inquiring about threading. In getting info you have to ask about the Sony UWP mics, and not the headphones, because the connectors are sold (and bought) for use with those lavalier mics. There's basically two common types you see--ones marked for Sennheiser and ones marked for Sony. But I've seen on some forums (the forums for the cousins to us headphone geeks over in the broadcast word) that the threading is actually the same, it's just that they need to be wired differently depending on whether you're using a Sony or Sennheiser mic. If that's really the case, then it doesn't matter which (Sony or Sennheiser compatible) you get. The people that say they're not compatible don't in fact specify whether it's the threading or the wiring scheme that's different, so they're no help.
I'm thinking of getting one, once I hear back about compatibility, and just not using the long metal housing. Instead, I'll figures something with a combination of plastic tubing and shrink wrap, and maybe something else, to emulate the molded design of our original cables, which seem less prone to damage from shocks than those long metal housings would be if they were sticking down off the 7520s.
So here are two types of connectors (actually 3, but note that these types aren't necessarily reflective of the Sony-Sennheiser distinction above -- I'm still trying to determine if the threading on these will fit the Sony, and which are of better quality generally):
Of course, there's also OPTION C:
Hope this helps!