One of the links above for foam is for neoprene. Do not buy neoprene. Blue foam is about 2lbs per cubic foot. Neoprene is more like 6. Its durable, but just too heavy for most applications. I do have a small quantity of neoprene if somebody wanted some.
Careful if you buy EVA. Being EVA foam doesnt guarantee its any better than blue foam. The quality can vary greatly. Foambymail is a site many dag players by foam from, and most are pretty happy with the results.
Those meijer blue mats are an example of poor quality EVA. The WAL MART blue mats are much, much more durable than those meijer mats. Dont buy them. The $6 WAL MART blue mats will work for just about anything if constructed properly. Almost every weapon failure ive ever had were from the glue wearing out, not the foam. Aside from stabbing tips, i dont think i've ever had the foam wear out or tear.