The ornamental design for the ribbon shaped balloon, as shown and described.
FIG. 1 is a front view of the ribbon-shaped balloon;
FIG. 2 is a rear view of the ribbon-shaped balloon;
FIG. 3 is a left-side view of the ribbon-shaped balloon;
FIG. 4 is a top view of the ribbon-shaped balloon;
FIG. 5 is a bottom view of the ribbon-shaped balloon; and,
FIG. 6 is a perspective view of the ribbon-shaped balloon.
The area defined by the inner ribbon outlines seen in FIGS. 1,2 and 6 is planar, all lines within this perimeter being representative of surface ornament rather than contour.