Atlas Model RR Co. produced the Ontario Northland National Steel Car plug-door 50' box cars in N scale and HO scale.
To get them in O scale from Atlas they would need to get a new O scale model produced somewhere.
Lionel could someday have these Ontario Northland plug-door 50' box cars made using the former Weaver Models Modern plug-door 50' box cars that are now in their LionScale line. It would take at least a year before they could get it produced.
Andrew