arty type) girlfriend of mine, used to get the stiff 'model makers' card from the Art shop. she used it for making small mock ups of the theatre sets (where she worked behind the scenes) Great little models, a la 'Jonathon Creek type' things. From memory the card seemed to be twice as thick as a cornflake box. Give it a try, I'm sure they would at least know where to get it even if they don't stock it.