Hello George,
Getting them etched will give a top-notch result, but if you want to 'do it yourself, it may be worth considering fretting the letters/numbers out of 16mm brass and sweating* them onto a background plate.
Neil
P.S. We want to see pictures of your loco!
*sweating = tin the back of the letters and front of the plate with soft solder, wiping the solder off with a cloth while molten (carefully!) then reheat with the letters in place, using a suitable pointed rod to adjust their position, if required.