The brass works well because it doesn?t interfere with the magnetic force.
I found a small (3mm) ultrabright LED that fits neatly in the tip of the index finger.
and a small magnet in tip of second finger.
The battery pack is home made out of plastic, screws, two 3 V batteries, contacts, etc.
The light is switched on by pointing with index finger and bring second finger to the base of the thumb.