AFAIK, the highest-concentration populations of both, at least in the US, are geographically semi-overlapping (the Bay is a magnet for both), so I'd be surprised if there isn't. Certainly I know many people who have similar interests to LW and who are also serious circus-arts people, though most of them prefer fire props to straight balls. I personally am at least a single-person overlap, though I don't consider myself to be at a high level in either.

As a sidenote, watching this video gave me a weird sense of how much my standards are distorted, because everything before about 2:30 in it looked totally pedestrian to me; I personally know a half-dozen people who could pull off everything up to that point.