Powdered Soy Sauce

Well....its the time of the season where I have to start thinking about getting supplies for the Dirty Duck at the Bristol Renaissance Fair. I cam across that companies has soy sauce that is in powdered form. We use soy sauce in some of the soups that we make at the Duck for the performers. A powdered form of this would be good for we have very limited space.

Has anyone seen this at any of the Asian markets here in chicago? I have tried both H-Mart as well as Assi in Niles with no avail. I would hate to order it online and find out that its not up to the standards that we need.

Mike