if you cant print it to scale , take it to kinko's or somewhere with a good copier. you can use any kind of plastic really , notebook covers and projector transparencies are the first that come to mind. print them on paper , adjusting the +/- resizing options until the thing is to scale. a lot of printers and computers use margins and headers and it can be a very big pita to get something consistently to scale.
once you have 1 inch coming up 1 inch , slip the plastic in , and get to it. just be careful , as laser printers use heat and toner , which can melt or warp your plastic.
thats why i just called a sign shop.he had some "10mil polyethelene" sheeting , which is actually 1mm . vetty vetty niiiice...
-hov