OEM OS disk for PowerEdge T320

Recently I've been given a PowerEdge T320 which had been retired from a local business who chose to retain the HDDs. From what I can see the server shipped with Win 2008 R2 Standard and I have the Microsoft COA shows the same. I was wondering if it's still possible to purchase whatever media (disk or thumb drive) that would have shipped with the server originally. Other than that, do I have any options reinstalling the factory-shipped OS?