I am in the UK and I have a minature tripod for a 35mm camera.

I want to attach something else to the tripod using the threaded bolt on
the tripod which normally goes into the body of the camera.

That bolt is about 1/4inch across and I have read that it has 20 threads
per inch, so it gets to be called "1/4-20".

I want a nut to fit this.

QUESTION: What would be the reference or specification for the correct
nut?

ISTR this threaded bolt is a slightly unusual size in Europe.

QUESTION: Can I get a bush to fit over the screwed bolt in order to be
able to get a more widley available nut?

QUESTION: Is there a common nut size (as far as Europe goes) which
might fit a bit loosely on the bolt but which could still be tightened?