Also, Whelen Engineering has some good choices. I installed both the HyperLite and the Whelen TIR3 on my bike. On the Whelen Engineering website, take a look at the choice of Lightheads. They make some nice products.

In addition, the TIR3 that I used fits perfectly in the space where the OEM passive reflector sits. The HyperLites can be mounted various ways. I made a special mount for mine which required cutting a hole in the fender but they can also be mounted on a license plate frame.