I assume you mean for the rear axle nut. I use a "hitch pin clip" (kinda shaped like an "R") instead. Works great. There's a whole thread on here somewhere with other options and pics.
A forum community dedicated to all Kawasaki motorcycles including the ZX-6R, KLR 650, Ninja 250, Ninja 250R, and Vulcan. Come join the discussion about performance, modifications, troubleshooting, maintenance, and more!