The ornamental design for a convertiblebag, as shown and described.
FIG. 1 depicts a front perspective view of a convertible bag showing our new design.
FIG. 2 depicts a rear side perspective view thereof;
FIG. 3 depicts a front side view thereof;
FIG. 4 depicts a rear side view thereof;
FIG. 5 depicts a first lateral side view thereof;
FIG. 6 depicts a second lateral side view thereof,
FIG. 7 depicts a bottom view thereof;
FIG. 8 depicts a top view thereof;
FIG. 9 depicts an internal perspective view thereof in, an open configuration; and,
FIG. 10 depicts an external perspective view thereof in an open configuration.
The broken lines showing the corners, handles, a snap button, and an external pocket with a zipper are intended to show portions of the convertible bag and form no part of the claim. All other broken lines shown on claimed surfaces are for the purpose of illustrating stitching and form no part of the claim.