Talked to my machinist yesterday. He said he'd be able to get them done in a couple of weeks on the outside.
In the meantime, I've given some thought to the switching issue and think it can be got around completely with a bit of a re-design.
In the original version, I'd included a couple of grooves machined in the handle to receive O rings to allow for a better grip.
Take that same idea, shorten the "plug" end to say, 3/8" or so, and include one or two machined grooves in it for O rings which would allow a friction grip in the first part of the headphone jack.
Perhaps two grooves which would allow for different overall diameters depending on how much "slop" is designed into a particular jack.