sorry about suggesting those lazer helmets - the lights are buil in which isn't what you wanted and also those lazer helmets are very expensive. i use a cheaper helmet, and i use velcro stickies to keep my small red flashers (from MEC) to the back of the helmet, and also i velcro a small white LED light to the visor.
the rear led is a bit trickier to properly direct the light as the helmet has those pointy bits that is a bit hard to aim the red blinky directly backwards and so the red light sort of flashes downwards than straight back. It sort of works out that the red light tends to light up my backback and sort of makes the backpack glow reddish.