The ornamental design for a bag with pocket, as shown and described.
FIG. 1 is a front perspective view of a bag with pocket according to my design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The short evenly spaced broken lines on claimed surfaces depict stitching that forms form no part of the claimed design. All other broken lines depict portions of the bag with pocket that form no part of the claimed design.