The ornamental design for a portablestoragedevice, as shown and described.
FIG. 1 is a perspective view of the portable storage device.
FIG. 2 is a perspective view with the portable storage device being open.
FIG. 3 is a front elevational view of the portable storage device.
FIG. 4 is a rear elevational view of the portable storage device.
FIG. 5 is a top plan view of the portable storage device.
FIG. 6 is a bottom plan view of the portable storage device.
FIG. 7 is a side elevational view of the portable storage device; and,
FIG. 8 is a side elevational view of the portable storage device.
The broken lines shown along the interior of the device in FIG. 2 represent the bounds of the claim. The remaining broken lines illustrate portions of the article. None of the broken lines forms part of the claimed design.