Here’s some info. In a worst case scenario, an old, even busted microwave will work as a faraday cage. Here’s a few links though, I can find more. Any grounded metal box will work to some degree, from my understanding, just keep whatever is inside insulated.
http://www.unitedstatesaction.com/emp_and_faraday_cages.htm
http://preparednesspro.wordpress.com/2009/06/18/emp-101-part-iv-faraday-cage/
http://www.youtube.com/watch?v=fQ_Z7LGZ1AM
Is a microwave considered insulated, or would I still wrap the items in insulation before putting them in the microwave?