I believe you are referring to the "Hidden River" yoke (Spring creek makes a yoke that doubles as a seat, Chosen Valley makes the aluminum tube pedestal yoke). My favorite no longer made solo yoke.
Here's photos of the angled brackets from that yoke.
That's 7" long- flange is 2.25" long. Width is 2.75"
I found the guy who bought the parts bin when Hidden River went under. I bought two sets of spare brackets. My initial pair failed after twenty some years of heavy use. I replaced the yoke with a Chosen Valley yoke, but I had three of them fail in three years so I went searching for parts.
Drop me an email if you want the email to the inheritor of the Hidden River parts.