Stereo usually only uses two cameras, is this for robotics use?
Perhaps you will want a shield that can control four. Or you could get external stepper drivers (not a shield) and run wires to them.
I searched for Arduino Uno motor shields for more than two stepper motors, but couldn't find any.
I have decided to go another simpler route: two stepper motors w/ timing pulleys and belts. With that said, I don't believe I'll be needing to hire anymore.