Webster OSV anti-siphon valve, $140 new
Like this:
https://www.zoro.com/webster-osva-38-oil-safety-valve-38-osva-38/i/G7008514/?utm_source=google&utm_medium=surfaces&utm_campaign=shopping%20feed&utm_content=free%20google%20shopping%20clicks&campaignid=21460994845&productid=G7008514&v=&gad_source=1&gclid=Cj0KCQiAvvO7BhC-ARIsAGFyToUmoK1alJJTv36NHvp5BsSixSrFfLKBDX0x_QmfALcDOh-jD2Cm0v8aApKcEALw_wcB&gclsrc=aw.ds