The Planet Bike SuperFlash is extremely bright. I don't know how it compares to a Dinotte, but at ~$20 each, you could buy three of them for less than half the Dinotte price.
Here's a real simple alternative. Buy a high power LED flashlight from someone like dealextreme.com. Get one that uses a 18650 Rechargeable battery and you'll get about 3 hours runtime on one battery. Purchase some red auto taillight repair tape (transparent) from an auto parts store. Cut out a circle to match the flashlight lens and stick it on. Mount the flashlight to your seatpost pointing back and blind approaching drivers.