I saw one fellow installed a head light using heat resistant wires, like used in a stove or other hot environment, to wire a under frame, tender, or cab mounted battery.
I made a Bachmann holding a plastic lantern into a lighted lantern. I drilled the base of the lantern into the clear lens area. Inserted a tiny LED into the lamp area. I soldered tiny wires to the LED and allowed the leads to make contact with two hearing aid batteries I pressed into the base. The lamp has no switch, but glows for about 18 hours. Just remove batteries when the light is to be turned off. Looking forward to completing the short line spur in Eugene, Oregon http://www.angelfire.com/or/trainguy http://community.webshots.com/user/raltzenthor ~Gary