The ornamental design for a storagedevice for electronic media, as shown and described.
FIG. 1 is a perspective view;
FIG. 2 is a top view;
FIG. 3 is a bottom view;
FIG. 4 is a short side view; and,
FIG. 5 is a long side view.
The stippling that can be seen on the claimed design is a type of shading that represents surface material. The broken lines are for environmental purposes only and form no part of the claimed design.