Ian
You can use 18 volt bulbs from LGB and wire them to the rails with MTS.
But, here is a better idea.
Find a string of Christmas tree lights, The small ones. You want the kind that if one goes out, they all go out (wired in series). If they are for 110 volts then 110 divided by 25 (the number of lights = 4.4 volts per bulb
That is about right for what we will do.
Now go to Radio Shack and buy some power diodes, The little black plastic ones, not the glass signal diodes.
Cut two lights out of the set so that you have two bulbs wired in series ( about 9 volts ), That’s perfect.
Make sure the bulbs are in series, like this ----------0------------------0---------------
Now attach one end to one of the leads of the diode.
(radio shack sells telephone splices that are perfect for doing this. just inset the wire in one end of the splice and a diode lead in the other end and crimp with pliers.)
Now your lights look like this ---------0--------------0-----------=-----[[[[]]]]-----
Turn off your track power.
Connect one end to one rail and the other end to the other rail.
Don’t worry about the polarity of the diode or the track.
Turn on the track power.
Are the light too bright or too dim?
Fine!
Now Select loco 0, That’s the address used to run unconverted locos, (you have decoders in all you loco’s I hope)
Turn the speed all the way up and watch the lights.
Reverse Loco 0 and turn the speed back down to zero.
Play with it till you get the right amount of brightness
Connect some more pairs of bulbs the same way.
You may notice that some lights get bright while others get dim. If that’s not what you want, then reverse the wires at the track.
As a last step, smear some of that LGB contact protector or rubber cement over the diode and splice.
Have fun.
B0B