Kawi part # 13144-1320 for the 16-tooth countershaft sprocket off the Z1000--a perfect fit for the 10 (2004-05 at least--I don't know about an '06).
And the countershaft bolt loosens counterclockwise. After you bend back the retaining washer, that is--otherwise, it doesn't loosen no matter which way you turn it. The whole job shouldn't take too long--under an hour--but you will definitely need someone to stand on the rear brake (tranny in neutral) and perhaps you may want to physically block the rear wheel from rotating as well . . . and a breaker bar will definitely be needed, if you're doing it without air-assisted tools.