This has been on my spa since the late 80's. The fitting that goes into the venturi system cracked. It is heal in place with a hoseclamp and then the ozone supply tubing screws onto it. It has male threads on that end. I can't find anything like it anywhere. It seems like there are no replacement parts available.

Try doing a search for "mazzei injector" or "ozone injector" and see if that is what you are looking for. If this is what you need I think I remember seeing one for about $35-50 but can't remember where. Shouldn't be too hard to find doing a internet search. Hope this helps.