Salty, the dry ice, cheap styrofoam route will definitely work. I have received several gifts of Omaha Steaks and that is how they pack everything, and the contents are always frozen solid. Even had one package sitting out in the heat for 2 days as we weren't home for a delivery and everything was still frozen.
Some grocery stores will stock dry ice from penguin.
try this link - hopefully it helps
http://www.airgas.com/customer_servi...ionType=DryIce