a person or a company that buys products from his/her local retailer or country on behalf of overseas importers.

Purchasing agents or buying agents are individuals or companies that offer to buy property or goods on behalf of somebody else. There are merchants for all sorts of products, from raw material commodities through to specialized custom equipment.
They buy products and services for organizations to use or market. They assess providers, negotiate contracts, and examine the quality of merchandise. Purchasing supervisors oversee the work of buyers and purchasing agents and usually manage more difficult procurement tasks.