Best Binoviewer: Reviews and Buying Guide - Little Astronomy
Amazon.com : Astromania Stereo Bino Viewer - Telescope Binocular Allows You to Adapt Two eyepieces to Your Telescope and View with Both Eyes simultaneously : Electronics
Orion Premium Linear BinoViewer for Telescopes
William Optics 1.25" Binoviewer with Eyepieces | OPT Telescopes