Looks like the Trek 5 LED blinky I bought with my bike (doesn't have an integrated reflector). The LBS took my rear reflector off when they installed the light. Of course after reading up on the law I realized a rear red reflector is required in California (and it has to be visible from a certain distance). Definitely check your state laws. Even if you only have to have one or the other, the more visible you are the better.

Mounting on a rear rack has already been mentioned. If you don't have a rear rack, maybe you could mount the light or the reflector on your left seatstay?