Does anyone know of a good place to buy a Hoffman Box online?

It seems more of a specialized device in little-known engineering/electronics stores. It is for testing the mobile apps we create in our company. We'd like to test to make sure it performs as expected when cell phone signal is lost.

Ideally, I'd like to block both Wifi and Cellphone (3G, CDMA) signals.

Ideally, price range is $100-$300.00. Although it is for my company so price might not be an object.