Lee,
Mike DeBerg who frequently posts on the 2-rail forum had these containers printed on thick card stock at this year’s Chicago O-Scale March Meet. The designs are by this company, DigCom Designs who have multiple refrigerated & non-refrrigerated container & trailer models for many scales except O-Scale. Mike was able to request & get the pdf files scaled up for O-Scale & he printed them on thick card stock, cut & glued them together. From a few feet away, I couldn’t tell that they were printed & folded until I held them close to my eyes.
For container trailers, there are highly detailed die-cast models of European container chassis in 1:50 scale available from EVOT-USA. Here are the links to their current offerings. I own the trailer in the second link. The front & rear ends of this model telescope allowing it to be used with both 1:48 scale & 1:50 scale containers, all the way from the shorter 20’ ISO containers like K-Line tank containers to longer Atlas-O 40’ containers. The main difference I have seen from container chassis trailers I have seen on US roads seems to be the wheel rims & markings on the rear bumper. Thankfully 20’ or 40’ ISO containers meant for standardized worldwide shipment means that the top & mounting areas on the trailer have to be the same.
https://www.evot-usa.com/product_p/wsi-17-0001.htm
https://www.evot-usa.com/product_p/wsi-03-1010.htm
These are just my opinion,
Thanks,
Naveen Rajan