Astro Systems 2" LightPipe/SightTube and 2" Autocollimator (f/4+)
Amazon.com : SVBONY SV121 Red Laser Collimator, Adjustable 1.25 inch Collimation Eyepiece, with 2 inches Adapter, Telescope Accessory for Newtonian Dobsonian Marca Telescope : Electronics
1.25" / 2" Laser Collimator for Telescope Reflectors (Collimatable)
Various Reviews, Page 5
AstroBeam II Barlowed Laser Collimator | Astromart
AstroSystems Archives - Sidereal Trading Pty Ltd - The Astronomy Store
Newtonian Telescope Collimation with theAstroSystems
DobSTUFF -- Center Donut for your Telescope Mirror