Hi
I made up these cardboard shipping containers for a personal project and am now selling them online.
They cost $9.82 for a set of 3 and postage to the USA is $2.89 for standard airmail or $6.35 if you want a tracking number.
There are more pics (and you can order) at
http://www.lasercutcard.co.za/scenery/shipping-container
**EDIT** These come as a kit laser-cut from cardboard and you have to assemble them yourself.
**EDIT2** Thanks lucasbuffalo

for spotting some possible ambiguity. These are meant for terrain, not to send models in. Unless you want to send your models in them. That's ok too.
Kind regards
Neal