The ornamental design for a wristband for an electronic device, as shown and described.
FIG. 1 is a first top perspective view of a wrist band for an electronic device showing our new design;
FIG. 2 is a first bottom perspective view thereof;
FIG. 3 is a second top perspective view thereof;
FIG. 4 is a second bottom perspective view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a side view thereof;
FIG. 8 is another side view thereof;
FIG. 9 is a front view thereof; and,
FIG. 10 is a rear view thereof.
The broken lines shown in FIGS. 1-10, which are immediately adjacent to the shaded areas, represent the bounds of the claim and form no part of the claimed design. All other broken lines illustrate environmental subject matter and form no part of the claimed design.