The ornamental design for a sidewall of a ribbon-shaped pill box, as shown and described.
FIG. 1 is a side, isometric view of a sidewall of a ribbon-shaped pill box showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a front view thereof; and,
FIG. 7 is a rear view thereof.
That which is depicted in solid lines in the drawings represent the claimed invention and that which is depicted in broken lines forms no part of the claimed invention.