Well, the first thing I would do is to find something on the shelf that is made locally and write down the contact information of the company...or just buy it, it's a little easier and you're helping out a local biz.
Write an e-mail, or call the company and ask what they did to get on the shelf. More than likely, they will be more than willing to help out, or at least tell you who you need to speak to at WalMart.