Three things:
Sorry, I forgot to mention that, of course, I'm willing to BUY the car kit from some kind soul, and...
I realize after looking at the manual for the 510, that it can't possibly work with my 410s because that model doesn't have the remote control/headphone combo input. But that's no big deal, it should work with the 505s, and...
The name of the thing that really makes it useful for the car is the Rotary Commander.
There, now I don't sound quite so stupid.
Thanks.
Tony R.
New York