I am not sure if yours was lexan or not. Why not check to see if SOB Or HOW store can get it for you. If lexan, you can purchase it but be aware of the cost. What ever you do, never use acetone around lexan and you can sand the edges with wet and dry sandpaper using water of course to smooth the edges. If buffing, low speed with a fine compound.
If you cannot get it there, check with a yard to see if they have a piece of scrap that big. A regular sheet is very expensive but it can be purchased from a yard, glass shop, etc..
For those who are looking for parts for your Hunter sailboats, you might try
www.shop.hunterowners.com/hp/index.php