34 AWG magnet wire is rated for 300mA and therefore should be usable for most applications in a locomotive.
I recently discovered TEMCO brand magnet wire.? They have an insulator that is designed to be removed by soldering.
34 AWG Copper Magnet Wire MW0085 - 2 oz Magnetic Coil Red Soderon 155
The price is reasonable, and shipping is free.
Best,
Ken Harstine
Holyoke, mA