I would eyeball the dac screw holes for size, go to Home Depot or a local hardware store, and pick up 4 or 5 different machine screw sizes. To narrow the search, Id be 99% sure theyre going to be metric, as its made overseas. Itll cost under a buck for all.
As an aside, just be careful of the length, in case a too-long screw may touch a wire or some other internal component inside the case.
Godspeed in your quest Bill.