If the street lights are not good enough for you to see I'd suggest getting something with at least 10w of light. The NightHawk Raptor comes to mind, it can be had for $50 or less.
If the street lighting is good enough for you to see but you just want to have a flasher so others will see you then just about any LED flasher will do the trick to be honest. I'm sure others will both agree and disagree with me.