"CC" wrote:

The description almost sounds like the male part of a rivet
They are often made of soft metals for ease of mashing
over the washer side.

The "washer" above is called a burr.

I wear a belt I made from nylon strapping material, bronze rings,
assembled with copper rivets and burrs.

Why the above construction?

No magnetic materials involved thus no affect on magnetic compass when
on the helm of a sailboat.

BTW, check a tool and die hardware supplier for the specialty bolt.

A long time ago, back in Cleveland, there was a company named Jergens
Tool who would have had what you need.

Don't even know if they are still in business.

Just Googled, yes they are still around.

Lew