Where do I obtain/purchase this item
That cable can be found included in the Mac Mini Dual Hard Drive Kit.
I'm sure the guy knew that. He was curious, as I am, to know where you can buy the cable itself. I don't want to pay iFixit's huge markup for some tools I already have and a glorified paper clip (I mean, "Logic Board Removal Tool").
Update: the part number is 922-9560, available for $30-40 online. If you don't already have the tools, the kit might not be a bad idea.