You could do a search at http://www.google.com/ and use the common name to find the botanical (Latin name) and then search with that.* I discovered the botanical name is Lycium barbarum.* Then search with terms such as:
Lycium barbarum + seed
This site has references for many mail order nurseries.* You might even be able to search by state and plant material, depending on what you are looking for.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.