I had the same experience with a local webshop here (bol.com). I needed two types of batteries but these webshops are more like marketplaces. They don't have a feature to search for items from a particular vendor. But I was able to simply browse and order the two types of batteries from a single vendor.

Next day: two packages. From the same vendor.

(Now that I think about it, the original sin was buying a product that is not rechargeable.)