What is this valve called? Where might I source one?

This is the fill valve on my aerator tank. It is purely mechanical and is operated by a pilot valve in the tank, that's what the black tubing is connected to. A while ago I had a problem with this main valve not shutting off so it didn't take me long to take it apart and figure out how it works. A simple but genius design lol. Anyway I cleaned the internal orifice that controls the thing and it was back to normal for several months.

Then it clogged again so I cleaned it again. No problems again for several months.

Clogged again today so I cleaned it again today. Back to normal but now it has a slight leak and I can't find this thing anywhere online. It's made by Nelson, so I'm guessing it's normally used for sprinkler systems.

Anyone know what this type of valve is called? I tried searching for pilot-operated fill valves but got nothing that looks like it.