TOPIC:

What 18" front fender from a Kawasaki application or other would fit my 77' KZ1000A's forks ?

I know upon advice from others on this Forum that it isn't advisable but like the 18" front wheel looks good.

Was focusing on a front fender from a Kawasaki triple 350/400 but maybe there are others ?

Airtech makes different sizes fiberglass ones. They don't have the mounting holes drilled in them so you would have to do that but they have a really nice KZ showing off a bunch of their parts on the website. You may also want a fork brace since I would think it would not be as stiff as the metal one but you can see if you need that. I moved my KZ around with no fender on it and the forks felt really wonky.

Like to find a steel one with integral brace. Look a little more period correct and stronger.

only 18" one l can think of is the 1978 Z1R D1, but they have those horrible support bars.
100% you'll need a brace if go fibreglass or plastic fender.