Who makes builder plates in HO scale, and where can I buy them? I'm in search for one to place on my 4-8-4 Northern, U.P. Greyhound (encircled in green).
You should be able to find either decals or dry transfers for those. I think the basis for that model is a Baldwin, so a search for Baldwins builders plate decals should turn something up.
Microscale has/had a set diesel data decals, that also happened to have builders plates that also matched steam locos plates. IIRC, PSC, Precision Scale Company, offers Steam loco builders plates in etched brass.