On the scrounge........Again!

Hi All
Anyone recall a locking device used to see them on fuel, hydraulic tanks, anything that had a screw on type lid?
If I can find one, may save me from having to make one.
The "NECK" of the filler spout is close to 70mm diameter-- the actual screw cap is close enough to 80mm diameter
The clamp part of the locking device was similar to a pipe clamp, had a pin where the two halves joined, once installed on the neck, another pin (or bolt with a dob of weld) secured it to the neck.
Once on it couldn't be removed because it wouldn't go past the threaded part.
The actual "locking bar" was also secured to a hinged pin, you folded it over so it was flush with the flat portion of it (the cap) and a tongue with a hole in it was used to put a small lock on.
Have seen something similar on an overhead fuel or chemical tank.
Very simple device, seemed to work OK, at least kept honest thieves out of the fuel.
Any clues or alternative suggestions appreciated, don't want to change the neck or filler.

Thanks, Dave_64

These are on Ebay under Fuel Anti-theft.

Similar idea, not EXACTLY what I had in mind, may do in a pinch though.
Thanks, Lang

Dave, You can buy a gadget ( It looked like a Strainer) that inserts in the Fuel tank Neck that stops desperados from siphoning out your Fuel. I saw one last time I was in a Kenworth Dealer. As they had some sitting on the Counter..

Dave,
Silly as it sounds I use a filter removal tool to give an extra tightening twist to the screw on caps used on the little Jap trucks.
Certainly can not unscrew them by hand.
Simple with no mods, needed.