1. A method comprising: receiving a request for a view product interface, the view product interface including a description of a primary product offered for sale by a seller, the view product interface indicating that a first item is for sale, the first item being an instance of the primary product; identifying a product bundle definition for the primary product, the product bundle definition specifying a plurality of secondary products selectable for purchase with the primary product; accessing, using one or more processors, inventory information of the seller, the inventory information specifying the availability of a second item, the second item being an instance of a secondary product of the plurality of secondary products; and providing the view product interface to the buyer, the view product interface including the description of the primary product and a description of the bundle, the description of the bundle including a description of the second item.