How can I buy packets of the mustard available at a Chinese restaurant?

The local Chinese restaurant that my wife and I eat at frequently offers packets of a wonderful Chinese mustard by W.Y. Industries. I’ve visited W.Y. Industries’ website but its not listed their for sale. Does anyone have any links to websites where I can buy packets of condiments like a restaurant would? Thanks a million.

Why not ask the owner or manager if they’ll sell you a box?