years ago there was an discussion about replacement taps for the Saturno in the german forum.
Just a few days ago one was searching again.
Unfortunately the added picture in the old article is broken.
Taps from Moto Guzzis V35-V65 and 850 GT should fit just like they are.
There should also be a gasket available.
Thread is M16x1
So maybe asking at your local Guzzi shop may give a help
ciao Joachim