As of next week I'll be commuting 2-3 days a week, which means I'll be on the road at about 6am - a good 45 minutes before sunrise. I have a headlamp that I use for night trail rides - I assume that will be good for the front, but I need a basic light in the back for saftety - any recommendations? Can I get away with something cheap/simple, or is there a reason to go with something a bit nicer/better?