The ornamental design for a multi-purpose bag, as shown and described.
FIG. 1 is a front, top, and right-side perspective view of a multi-purpose bag;
FIG. 2 is a front-elevational view of the multi-purpose bag;
FIG. 3 is a rear-elevational view of the multi-purpose bag;
FIG. 4 is a right-side-elevational view of the multi-purpose bag;
FIG. 5 is a left-side-elevational view of the multi-purpose bag;
FIG. 6 is a top-plan view of the multi-purpose bag; and,
FIG. 7 is a bottom-plan view of the multi-purpose bag.
The broken lines shown in the drawings are shown for illustrative purposes only and form no part of the claimed design. In addition, the surface shading, if any, illustrated in the drawings is provided to highlight the contour of the design and, as applicable, to be illustrative of texture.