Science Fair Display Board Help

<p>I have made my poster for the science fair and it is 48'' by 36''. The problem, however, is that it is one flat sheet of paper and cannot fit on a three-panel display board (because three panel display boards bend)</p>

<p>At the science fair, I need to somehow prop up my poster but I can't seem to find flat foam boards this size. </p>

<p>Any ideas?</p>