The ornamental design for a protective cushionattachment for a shopping cart seat, as shown and described.
FIG. 1 is a perspective view of a protective cushion attachment for a
shopping cart seat showing my new design, the broken-line disclosure of a
portion of the shopping cart being for illustrative purposes only and
forming no part of the claimed design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a right side elevational view thereof, the left side being a
mirror image of that shown; and