I built my own 12v 20w halogen bike light. It was really pretty easy. I bought a 4.8ah lithium ion battery from batteryspace.com that came with a charger for $95. Not cheap but much lighter than SLA. I put the battery in a small camera case and velcro'd it to the bottom of my stem. I then used a short section of copper pipe and gorilla glued a mr16 halogen bulb in one end. I soldered wires to the bulb and ran them out the back. Connect to the battery through a switch and done. I use a twofish flashlight mount to hold the light to my handlebars. I have built a few of these lights as I get more ideas about the construction. I have yet to burn out a bulb but I carry a spare in my panniers. Each light is about $10 but you could build them for much less if you shop around. If one were to break I would just throw it away.