The ornamental design for an attachmentpocket, as shown and described.
FIG. 1 is a perspective view of an attachment pocket incorporating our new design;
FIG. 2 is a front view thereof.
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
All of the broken lines shown in the drawings illustrate portions of the attachment pocket and form no part of the claimed design. The shaded features and solid lines shown through the broken lines illustrate the claimed surfaces of the attachment pocket.