Electronic commerce applications are lacking a bilateral negotiation model which provides the bargaining between two participants (supplier and consumer) in order to buy and sell goods. This paper proposes a negotiation protocol between two participants, as well as the similarity measures which were implemented to find a similar product, when a specific one could not be found. The proposed protocol follows the bilateral model approved by the OMG. The negotiation model is composed of selling and buying Grasshopper mobile agents which negotiate between them in order to get the best deal. The negotiation of the price is based on the Kasbah model. The catalogs in the model are implemented in XML to provide the interoperability among different systems. A simple prototype has been implemented to verify the viability of this concept.