I've had a CatEye TL-LD1100 mounted to a rack for years and years. It screws right to the rack using the rack's standard reflector bracket, and the screw comes in the package.

It even survived a crash that bent the rack. None of that falling apart crap you get with the Superflash. (EDIT: Come to think of it, it's survived two crashes unscathed. The first when we went down due to rider error, and the second when we were left-crossed by a Pontiac. Both times road impact bent the rack.)

You can see the scratches on the rack from the first crash.