Return stock for different vendors

Hello,

I have the following scenario:

The customer returns an article 1 to the wholesaler (DC). An employee decides that the article 1 should be shipped back to the vendor X. To save shipping cost the shipment will only be done after enough articles are on storage location.  There is only one storage location for several articles (e.g. 1, 2, 3 ...) from several vendors (e.g. X, Y, Z).

Now my client wants to know, which article on the storage locations are going to which vendor.

I tried to think of different storage locations for vendors, but that is not an option.

Also I was thinking of consignment stock, but this doesn't work because the financial booking is only allowed after the goods are shipped back to the vendor (posting GI).

Do you have any smart ideas how to handle this scenario?

Kind regards,

Frank