Charlie, would pipe clamps do...? They come in 1/2" and 3/4" pipe. Heavier than the Bessey's or Irwin's but will do the job.
Example 3/4"... https://www.rockler.com/sure-foot-plus-3-4-pipe-clamp
Example 3/4"... https://www.rockler.com/sure-foot-plus-3-4-pipe-clamp