You can probably make this at home, to check the alignment of your chain and sprocket. It's basically a bracket that goes onto your rear sprocket then a long thin rod as a reference line to see if your chain is properly aligned.

http://www.motorcycle-superstore.com/ProductImages/300/633010776712874239CHAINALGN.jpg

http://indysuperbike.com/img/MotionPro/chainalign.jpg