Lost shipments – how to provide an invoice?

Amazon has lost a few of our shipments and needs the invoices for proof of ownership. The problem is we do not currently ship directly from our manufacturer to Amazon and so there isn’t a 1:1 invoice for the shipment we send to Amazon.

We order from our manufacturer in bulk, bring the product into our US warehouse, break it down into smaller quantities, and repackage some into bulk/variety packages.

How do you provide an invoice in this case?