On my button boxes, I use the MicroVox system---

http://www.buttonbox.com/accessry.shtml

Bar mic on the right, velcro'd on, on the left, a littler mic: the two
go out to a preamp-box, which I then feed with a stub cable to a
wireless box--- both sit on my belt above my arse.

The wireless box goes into a DI for the sound guy.

This sounds complicated, but it isn't--- I can change instruments
and just slap the mics onto the pre-velcro'd spots.

And, I'm really wireless, and properly balanced, bass and treble.

So I can jump out into the aisle if I want, and still be properly
mic'd.

Beats the hell out of a couple of SM-whatevers where the bass
side is going from 1 to 16 inches and I'm locked into the treble
side and getting whiplash from trying to stay in the right location
re: the vocal mic.

Not cheap.

Well worth it.