Acrylic (perspex) is very expensive: http://pages.ebay.com/link/?nav=item.view&id=301128378071&alt=web
I imagine glass would be far too fragile. You might be able to laminate thinner sheets of acrylic to the required thickness, still won't be very cheap though...
I imagine glass would be far too fragile. You might be able to laminate thinner sheets of acrylic to the required thickness, still won't be very cheap though...