The ornamental design for footwear sole piece, as shown and described.
FIG. 1 is a front perspective view of the footwear sole piece showing my new design;
FIG. 2 is a left side view of the footwear sole piece shown in FIG. 1;
FIG. 3 is a right side view of the footwear sole piece shown in FIG. 1;
FIG. 4 is a front view of the footwear sole piece shown in FIG. 1;
FIG. 5 is a rear view of the footwear sole piece shown in FIG. 1; and,
FIG. 6 is a top view of the footwear sole piece shown in FIG. 1.
The broken line showing of the heel, portion of sole, heel cap, buckle, buckle holes, straps, footbed and body of the footwear is for illustrative purposes only and forms no part of the claimed design.