I'm trying to balance my camera on a monopod with tons of stuff attached (light, shotgun, wireless receiver, mattebox etc) as part of an experiment that will eventually lead to a handheld stabilizer. I've seen balance plates with easy L/R and F/B knobs mounted on steadycam type sleds and I was hoping that such plates are available without the rest of the rig. I have found many plates that balance front to back but none that balance in both directions. But they must be out there because I have seen them.
Unless you have one custom made, or buy a glidecam and use that stage, the closest thing I have seen is to use 2 manfroto slider plates at an xy angle to each other.