MPM35 - A trip to Active Surplus

I found a new material to work with on my trip to Active surplus. It's called Lexan. It was affordable and there was a lot in stock, so I took advantage and bought 10 sheets. The pieces are about 3 x 3 which I feel are large enough to create the effect I want. However, they are flimsey (as u can see by the way im bending it in the picture) and I am thinking about creating a border out of a thicker plastic so that they can stand like in my previous sketch.

I still haven't figured out what I will use to represent each child missing. Since it will be a large number I have been looking around printing shops, but no one seems to be able to print that large on the sheets that I have.