Peter (Peter_4059) and many others on the web have kindly shared their binocular mounting designs for all to see, so I've included some images of a rig I've assembled this year from an old unused Tasco 4.5" reflector tripod mount/bearing, some metal parts from Bunnings, and a metal binocular mount from Andrews. The metal bars and plates are separated by milk-bottle washers, ala Peter. The counterweight shaft had me stumped until I noticed an old broken microphone stand lying around at home - "that'll do!".
The tripod isn't overly strong or sturdy, particularly for twisting vibrations, but doing this saved me having to make a swivel bearing or buy something suitable. I'm pleased to say the whole rig was a pleasure to use at its first dark sky outing at Leyburn recently. A little settling vibration is present, but its really inconsequential compared to the endless wobbles when hand holding. I've never had such good binoc views, and am looking forward to doing some more touring between imaging sessions at Astrofest. You have to jump about with your chair a bit of course, but decent swathes of the Milky Way can be explored without too much moving around, and I'm particularly pleased I took the extra trouble to build additional movement into the end mounting for this purpose. Happy to provide measurements, parts, prices detail for anyone wanting more detail.
More pics here for those interested:
p.s. Thanks to Peter Ridgeway for giving me a couple of spare old 5kg counterweights with my last astro-purchase