For nighttime use or just daylight?

You might take a look at the Bontrager Flare ION's or just the Flare's themselves if you'd be amicable to a longer light on the bars. The smaller ION's might not have the lumens you are looking for but for daytime use they are more than bright enough to attract attention, IMO.

Some of them can even be turned on/off and flash pattern controlled by a GPS device.