Materials:

Battery pack - $20. Auto parts supply (Pep Boys,) used as portable alternate power source for powering tools, boosting weak batteries, etc. Sealed non-spillable lead-acid 12v, 5 amp/hr rechargeable battery in padded, water-resistant case, with 110v charger, car battery charger for on the road.

Malibu outdoor yard light - $12. Home improvement/hardware store (Home Depot,) 12 volt, 20 watt halogen light, black aluminum housing, adjustable verticle beam angle, glass cover. Can be upgraded to a higher-watt bulb.

Cable ties ("zip-ties.") - "in the house." (1 penny?) Any hardware store. Used to tie the wire to the bike frame.

Hose clamps - "in the house." ($1?) Any hardware store. Used to attach light to handlebar.

Wire connectors, electrician's tape - "in the house." ($1?) Any hardware store. Used to connect light wires to battery wires.