This is something one with a decent set of skills could make in Adobe Illustrator or a similar vector editing program.
I could actually do it given enough time, but to be frank I don't quite have that kind of time on my hands these days.
Also, this reminds me: I told kitsch I'd work on a clear screen cover template file, so I should really do that. Doing that would be 80% of the work of recreating a vector of the DMG screen cover graphic.