You can talk to your local Wal-Mart about special ordering some blue foam for you. If you want to just order some better foam, you can use shops such as foamforyou.com, and order their 2# roll foam (volara). It's more expensive than blue foam, but also more consistent in quality and longer lasting.
With those kind of orders, it's best to try and find a shop that may be near you, or to do a large order, as shipping can be rather high.
Alternatively, you could order blade kits from shops such as
Forged Foam or
Foametheus.