The ornamental design for a waistbandexpander, as shown and described.
FIG. 1 is a perspective view of a waistband expander, showing my new design in a condition of use;
FIG. 2 is an enlarged perspective view thereof;
FIG. 3 is a front elevational view of FIG. 2;
FIG. 4 is a rear elevational view of FIG. 2;
FIG. 5 is a left-side elevational view of FIG. 2;
FIG. 6 is a rear elevational view of FIG. 2;
FIG. 7 is a top plan view of FIG. 2; and,
FIG. 8 is a bottom plan view of FIG. 2.
The dot-dash broken lines showing a pair of pants and a hook implement in FIG. 1 depict environmental matter and form no part of the claimed design. The dot-dash broken lines showing the centrally-located button hole form no part of the claimed design. The remaining broken lines represent stitching, and are part of the claimed design.