I was at the HoB in Las Vegas a couple of years ago (saw George Thoroughgood and the Destroyers - great show, BTW).
A couple of things:
- at the LV location they had many security guards with wands checking everyone before they came in, and they were checking jacket pockets and purses. A Zorki 4 is very metallic, I doubt you could get by with one.
- despite the no-camera rule, people tried to take cell phone pics. Inside they were more security guards, who seemed to be watching for this. If they saw someone trying, they would shine a flashlight on their camera, and when they looked up they were given a stern look. I think the guards approached a couple of persistent offenders to scold them, but I don't think anyone was ejected for that specifically.
I wouldn't risk it, personally. The only mostly-plastic film cameras that I'm aware of are fixed lens and/or no-focus - even with a high-speed film I doubt you'll get in close enough.
I'm not familiar with Matt & Kim, but if they're still small enough, why not ask their management if you can take pics "officially", and get an official pass for the event/venue? Then you wouldn't have to worry about getting caught.