Not knowing the
system they use, I can't say for sure, but the first two companies to look at are
telex and Clearcomm. You have to make sure the
system you're getting will interface with their wired
system. The pin setups are different between the different brands.
On another note, this is going to be reallly expensive. You have to get a wireless
base as well as a wireless
beltpack and potentially something to interface the wireless and wired systems. I just say this in case you're buying it yourself. It's probably not a great
purchase for just a couple shows.
I don't see a big reason for most SMs to go wireless, but I've known quite a few ASMs with the tethered blues. The easiest fix, rather than going wireless is to just setup a ton of backstage beltpacks. I imagine that's probably more doable than going wireless.
Lastly, I've seen comm equipment on ebay, but if new is your thing check Full
Compass and other audio distributors.