The ornamental design for a portion of a shoe upper, as shown and described.
FIG. 1 is a top view of a portion of a shoe upper;
FIG. 2 is another top view of the portion of a shoe upper;
FIG. 3 is a first perspective view of the portion of a shoe upper; and,
FIG. 4 is a second perspective view of the portion of a shoe upper.
A portion of a shoe upper is shown in FIGS. 1-4. Dashed lines have been included for illustrative purposes only, and form no part of the claimed design.