Sonos shows the swingarm w/ beam mount on their site:
[Link: sonos.com]

I've emailed Flexson multiple times looking for the beam-only mount (no swingarm mount): [Link: flexson.com]
I get no response.
Apparently Sanus will have a beam mount, but not yet: [Link: sanus.com]

I've used the Sonos Beam wall mount in conjunction with a universal soundbar mount a couple times. I'd much prefer a better option - I'm waiting for availability from Sanus, Flexson or anyone else with a cleaner solution.