Good question! I rock one of my cats, but that's because he likes it, not because I do. (Well.. I DO, but that's beside the point.)
If you're looking for visual cues you can give people that will make them ease up and let you rock, one of the easiest is headphones. I swear if you're wearing head phones all manner of things are magically excused, including ignoring the people around you. One of my favorites when I need space.
But if someone said you could only rock a baby in a rocking chair? I'd come straight back with, "Hey, I'm so good I don't need a special chair. Me? I can rock anywhere, any time. Try to keep up."
(This is meant to be semi serious because I'm only half joking)