I found a post on the 3 rail side that mentioned some diecast containers that might work for O gauge. Turns out the containers referenced are too small for O gauge but look pretty good for S gauge.
The OP measured the containers he received and the dimensions were H: 1.60" W: 1.46" L: 5.1875". The OP also said "They are die cast metal, weighing about 7.675 OZ each. The end doors open easily and the details are crisp."
As the purchase price was pretty reasonable compared to containers from Des Plaines hobby at about $25.00 each I decided to check it out.
The measurements given scale out in S gauge to 8.5' High, 7 3/4 ' wide, and 27.66' Long. That's kinda off compared to standard 20', 40',45',48' and 53' containers. But hey they might look OK stacked one on top another in an S gauge well car.
Fellow S gauge forum member MIKEAA also found these containers in the original post as he commented on that post also. Those were $8.90 each with free shipping.
Adding about 15 oz (2 containers) to a well car would make for a heavy load but it would probably ride pretty steady with all that weight and a low center of gravity.
I still haven't ordered any well cars from DEP as I'm waiting for a sale. These containers look pretty good though and the price is right.
Just thought I'd share my discovery with the group.
Mark