The ornamental design for a portablestoragecontainer, as shown and described.
FIG. 1 is a perspective view of the portable storage container;
FIG. 2 is a front elevational view of the portable storage container;
FIG. 3 is a rear elevational view of the portable storage container;
FIG. 4 is a right side elevational view of the portable storage container, the left side elevational view being a mirror image of the right side elevational view shown; and,
FIG. 5 is a top plan view of the portable storage container.
The bottom view is not visible in use and forms no part of the claimed design. The broken lines shown in FIGS. 1, 3, 4 and 5 illustrate portions of the article which form no part of the claimed design.