VHF antenna mount adapter

Ham radio operators often need a simple way to mount a small VHF or UHF antenna for testing and tuning, or for 'Field Day' type operations. Many locations will have a chain link fence on the property and the corner posts are steel with a metal cap that is just hammered onto the pipe. Antennas have bolts and clamps for standard TV mast mount, which is nominal 1-1/4" or 34mm OD tubing. Mast will drop into the fence posts, but the fit is very loose and the antenna will not be stable wit