Airmont Products AP-10921, Heavy Duty Adjustable Porcelain Wire Holder, Reinforced Steel Saddle, Adjustable Steel Clamp Fits Around Any Pipe or Pole, Ceramic Head for Cables or Wires as an Insulator - Amazon.com
Sigma ProConnex Steel Clamp-on Type Service Entrance Wireholder Conduit Fittings in the Conduit Fittings department at Lowes.com
Halex 1-1/4 in. - 3 in. Service Entrance (SE) Adjustable Wire Holder 60525 - The Home Depot