Partzilla has diagrams w a cross-reference. Find your motorcycle, choose a diagram, then click the part for the x-ref.
Kawasaki.com also has the diagrams, but partzilla is easier to use. some items are still available from the dealer. usually maintenance stuff.
What I do is search a part number on EB to see if NOS is available as photos of new parts are handy. then I search by basic model w part name & alternate name. In some cases NOS is preferable & not much more expensive than good used. however, many nos parts seem to be priced kind of high on EB nowadays, though.
For some parts you don't have to get oem. handlebars & grips. flasher relay. starter solenoid. shocks. I like the stock grips, so I got nos oem. The auto parts store has direct swap Novita electronic flashers which are made or assembled in USA . Z1Enterprises.com should have some items. I've been getting stuff from them for quite a few years. Fork oil. brake lines. handlebars. oil filters & other maintenance type stuff.