Branchline - then - Atlas did a very nice HO model of the mid-1950's GARX insulated plug-door box car - the one with the horizontal rib.
I'd love one in N scale, but doubt it's going to be commercially available anytime soon. The producers of new freight car styles are concentrating on much newer and more common cars. I'm not going to learn CAD just to get one printed either. But, I might try and kitbash something close. I figure if it's close enough someone will come out with a commercial model of it!
Has anyone investigated doing a kitbash? I figure the horizontal rib will have to be an added detail on top of some other sides.
Here's the car (from Atlas catalog art)
The roof and ends of the Micro-trains riveted side mechanical reefer look pretty close, but the sides and door aren't right at all. Definitely kitbashing to be done!