How would I go about determining the final shipping costs for an inbound shipment?

I know it’s possible to get the estimated cost from GetTransportContent, but I want the finalized costs. I looked at pulling the settlement reports, but the data I get back doesn’t contain a unique ID I can use to map back to a shipmentId it just lists the date, FBAInboundTransportationFee and the amount…

So how do I map the actual cost of a shipment to the shipment itself reliably?