Your local sign shop has scrap chloroplast to test fire at or you can just take my word for it that it will split and crack with every hit and have to be replaced just about every game...
Search "polycarbonate twin wall" Quite a few suppliers. Link to one.
If you can't find it locally, Fed Ex will ship 4'x5' panels as an oversized package. You can put 8-10 sheets in the box max width allowed. Shipped for about $50 since it doesn't weigh anything.
Email or pm for info as needed.