Call Dave at NWSL - he will know which size.
NWSL sells a screw/nut/bolt variety pack with most of the common brass sizes. I bought one years ago and it has come in handy on lots of occasions.
Guy
see stuff at: the Willoughby Line Site
They're metric, Tom. If you have a micrometer or dial caliper, you could check the diameter of a similar screw and try your LHS. That's how I got the screws for my O scale Atlas bobber caboose coupler box screws--from a local dealer who handles RC cars and planes.
Deano
I have lost the coupler box mounting screws for my PFM Omaha 0-6-0. I have tried 0-80 screws and not correct thread size. Anyone know the correct thread size?
Tom