Venturi air valve on Berlin skimmer

[Delphinus]

Are you referring to the nylon screw that presses on the airline?

I'm sure you could find a replacement screw at Home Depot. Or Big Al's, or Pisces.

I don't use mine though. I use a dripline irrigation valve instead at the inlet of the airline. A good valve of this nature will allow for much more fine control that squeezing the airline. You can get this at Rona and HD, too. Another thing to consider is that the screw pressing in on the tube can eventually cut into your airline.