The ornamental design for a portion of an inputdevice, as shown and described.
FIG. 1 is a front perspective view of a portion of an input device showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken line showing of various regions in the figures, including the unshaded areas therein, is included for the purpose of illustrating unclaimed portions of the article and forms no part of the claimed design.