The ornamental design for the surface pattern for a portion of a knitted garment, as shown and described.
FIG. 1 illustrates a front view of a surface pattern for a portion of a knitted garment incorporating a surface pattern in accordance with the invention; and,
FIG. 2 illustrates a rear view of a surface pattern for a portion of a knitted garment of FIG. 1 with the surface pattern in accordance with the invention.
The broken line showing of the knitted garment is for illustrative purposes only and forms no part of the claimed design.