What about a stealth hat? Honestly, the security will not be looking for anyone who is taping a sound check so don't get all nervous about it. Poke around here for some stealth hat ideas, there's quite a few options: baseball forward, baseball backward, beanie, kangol, cowboy... When people think of microphones they think of the things on stage, not the tiny little things you have, so security won't exactly be looking through the people there for someone wearing tiny mics. Listen to Moke though cuz a croakie is probably the easiest way to hide your mics and the wires without sacrificing mic position or sound quality. However, you'll look either like someone heading to a nascar event or a secret service member!
Who are you taping anyway?