The triple bearings are the same from the 83-04 so you could use any year forks as long as you get the matching triple clamp.
The problem is your 17mm front axle size which went to 20mm in 1994.
The other problem is your outside to outside bearing dimension which is 102mm.
You could use your front wheel up to 1993 but anything past 1988 would require new shorter wheel spacers.
Your next problem is your brake mounts, they won't work with anything newer.
You can find sizes and years here:
http://oem-cycle.com/KAWASAKIKX500BIKEID.shtmlJust scroll down and way to the right.
Basically, your way better off finding a complete front end.
So... you could get a new steering stem adapter and replace your entire front end with a 2014 KX450F front end .
As the saying goes, it's only money