The G.S.L.
You may or may not know about the Golden Spatula League.
They are the greatest agency of catering detectives in existence. Who else can access the most dangerous people on the planet? Not the police. Not regular detectives. Not government spies.
But waiters will. Chefs will. Kebab vendors will. And of course, pizza delivery boys will.

The G.S.L. was founded in 1867 by Rudolph Tapsav, a Swiss chocolatier and part-time detective. Rapidly expanding into an international network, today the G.S.L. can be found in most countries in the world. (They are in talks with Andorra.)
To find them, you should look very closely, on drawers, doors and drains, probably with a magnifying glass, for the special G.S.L. symbol:

But don’t try to contact them. They will contact you.