The ornamental design for a poweradapter for an electronic device, as shown and described.
FIG. 1 is a perspective view of a power adapter for an electronic device showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines shown in FIGS. 1–7 that are immediately adjacent to the shaded areas represent the bound of the claimed design, while all other broken lines are directed to environment and are for illustrative purposes only; the broken lines form no part of the claim design.