I believe that’s a simple Quick Disconnect fitting, he mentions holding it on the post as it fit’s the diameter, but doesn’t lock. I do something similar, but have it fitted to a standard ball-lock, plus 40 psi is crazy cool pressure, I wish I had that…
Yea, it’s just a simple ball lock brass QD that I purchased at my local Lowes. In a stroke of luck they fit great! (almost) I can’t find these anymore. I have 12 sets for Brutus but I need one or two more really to match… I would suggest just taking one of your keg post to Home Depot or Lowes and see if you can find one that fits.
I would imagine that 40 psi would help depress the popet valve as well if held tightly, I am not sure I could pull that off with my enlarged prostate water pressure ;D