I did eCommerce order tracking, and for the products tracking inside the order, I used following code snippet.
_paq.push(['addEcommerceItem',
"123456789", // (required) SKU: Product unique identifier
product_name // (optional) Product name
[" "], // list of categories
product_price, // (Recommended) Product Price
1 // (Optional - Defaults to 1 quantity)
]);
So in the above code, I can concatenate the vendor name with product name and on reporting side I can use the contains operator to filter the specific vendors’ products.
You could try the solution suggested by @Naser_Aslam or you could use a custom dimension and pass the name of the vendor along with the visit, so that it is possible to filter the data based on vendor.