The ornamental design for a strapping for a handbag, as shown.
FIGS. 1-8 show an embodiment of the strapping for a handbag of my design;
FIG. 1 is a perspective view of a handbag with strapping showing my design taken from a top left side;
FIG. 2 is a front perspective view thereof;
FIG. 3 is a rear perspective view thereof;
FIG. 4 is a right perspective view thereof;
FIG. 5 is a left perspective view thereof;
FIG. 6 is a top perspective view thereof;
FIG. 7 is a bottom perspective view thereof; and,
FIG. 8 is perspective view thereof taken from a top left side and showing the strapping for the handbag with the handbag in an open position.
The broken lines showing stitching and portions of the handbag are for the purposes of illustrating environment and forms no part of the claimed design.