Cheap Cycle Parts is the cheapest place I've found so far for Kawasaki OEM parts, compare to Bike Bandit and 2 other places.

http://www.cheapcycleparts.com/pages/parts/viewbybrand/default.aspx

The Ninja 250 model number starts with EX250, then a few suffix after that indicating the year.

link should be updated since it dosnt work any more and then it should be stickeyd or pined uptop