Actually, because of this project, I have found a couple of sources for RS-3 numberboards as well. They came in different versions depending on how many spaces there were for the digits. The B&M ones you mentioned were 4 digits, which I have. I needed the 5 digit ones(for MEC RS-3s), which JnJ makes, as well a 3 digit. I think my 4 digit ones were from Minis by Eric or Detail Associates.