I claim the ornamental design for a towel bag, as shown and described.
FIG. 1 shows a bottom view of a towel bag in an unfolded configuration;
FIG. 2 shows a top view of the towel bag in the unfolded configuration;
FIG. 3 shows a rear view of the towel bag in the unfolded configuration;
FIG. 4 shows a front view of the towel bag in the unfolded configuration;
FIG. 5 shows a left view of the towel bag in the unfolded configuration;
FIG. 6 shows a right view of the towel bag in the unfolded configuration;
FIG. 7 shows a front view of the towel bag in a half-fold configuration wherein the towel bag is folded in half along an imaginary vertical axis.
FIG. 8 shows a front view of the towel bag in an eighth-fold configuration wherein the towel bag is folded in one-eighth; and,
FIG. 9 shows a perspective view of the towel bag in a cinched configuration.
The stipple shading disclosed on the surface of the towel bag represents material and extends across the entirety of the tote surfaces, and forms part of the claimed design. The dashed shading on the strap of the towel bag represents hook and loop material, and forms part of the claimed design.