I can't tell if it actually has holes for mounting, and is essentially the same thing as what you have a photo of, except without the plastic housing. I don't know if that will help you, but is what I am considering.
From what I can tell on a slightly more detailed picture on their web-site, it does not look like the adapter has holes for screws/mounting.
However, I think you might be able to place 2 screws on each side, and perhaps 1 or 2 behind the holder - or - modify the PCB sligthly (eg. make a notch), so that one screw can hold it in place on one side.