Thanks everybody for your replies. I had a look into the various options suggested here, and since it'll be hanging over people's heads and in quite a noisy environment, I opted for the Doughty modular system - a clamp, an adjustable drop pole and a single stirrup on the end, then couplers attached to the cameras.
For those asking, they're Datavideo PTC-150s, meaning their screw threads are all in US/Imperial sizes, so next headache is finding the right bolt, but thanks all for your help, I really appreciate it.