Thats a tricky one, i would be cheaper to buy a full sheet and cut it up yourself... perspex it flexible and cheap, prone to scratching, melting and snapping depending on its use...
you would want at least 4.5mm colour wouldnt matter, but clear is cheapest - and we sell sheets of 1220 x 2440 4.5mm clear for $200.00
it would do the job, but if you look toward the future, a metal one would be better, but if put together right, a perspex one woudl rock!