Well, hopefully somewhere you wrote down the key code number (on Ninja Boy it was on a metal tag on the key ring.) That is the ONLY way Kawasaki or a dealer can make a replacement key. They cannot duplicate or replace a key without the code number.
If you do not have the code number you will have to replace the ignition switch AND the rear seat lock.
My spare key and the metal tag are in a safe place at home and I also wrote down the code in the owner's manual.
I have come to terms with the possibility of dying while riding, life has a 100% death rate. I would rather live having fun and end up dead in a motorcycle crash than never do anything fun because it's dangerous and I might get killed. No one makes it out alive anyway. - From a friend on another forum, used with his permission.