For a dirtbag quick-fix for those after work rides that might finish up after sunset, I just wrap an old headlamp around the bars and stem. Works great, plenty of light, has a flasher mode too. For the rear red light, I clip a lightweight flasher on my jersey pocket. I think I got it free somewhere. The headlamp uses two AA rechargeable batteries, so total cost for my low-end but effective "lighting system" is virtually nil. Plus, if I need light to change a flat or something, I can just unwrap the headlamp and use it as ... a headlamp!