Hi

just place an air winded coil around a reed "bulb" ... 10-15 turns * amp ( 20 - 30 turns for 1/2 amp ... 5 - 8 turns for 2 amps.)

in SERIES with your lamp.

reed contacts close when current flows.

Maaaaaagic, you told Maaaaaagic ???

circuits insulation as a bonus ... what else needed ???

Alain