I quite like my Fizik saddle with ICS bracket. A number of Cateye lights are compatible with it. It holds the light steady, no ugly brackets and it puts the light as high as possible so dopey motorists can see it.
I can't recommend the particular light in the picture. I had one and the battery compartment tabs eventually broke rendering the light useless. I now have a usb rechargeable cateye Rapid 2.