The ornamental design for portable electronic device, as shown and described.
FIG. 1 is a perspective view of a first embodiment of a portable electronic device with a brushed finish surface pattern, showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a perspective view of a second embodiment of a portable electronic device with a brushed finish surface pattern; and,
FIG. 4 is a top plan view thereof.
The broken line showing illustrates portions of the portable electronic device which form no part of the claimed design. The top surface has a brushed finish pattern.