I bought a set from a random Chinese seller.
A pair Brake Clutch Levers Fit For KAWASAKI GPZ500S/EX500R NINJA 1990-2009 CNC is the exact one I ordered. They were $24.95 with free shipping November '13.
They have random machining marks on them. As opposed to a nice consistent pattern all the way across or perfectly smooth, the lines run different ways on different sections. You can't even feel them dragging your fingernail over it, but you can see them in the light. Minor aesthetic thing.
They installed quickly and easily on my 500. It took me longer to get my tools out than to put them on.
I just put them on near the end of winter and have only been able to ride a few times. So far I like them and don't foresee any issues.