The ornamental design for an seamportion of a seat for a vehicle, as shown and described.
FIG. 1 is a front view of an seam portion of a seat for a vehicle showing our new design;
FIG. 2 is a perspective view showing the environment in which the ornamental portion disclosed in FIG. 1 is applied to, the view being observed from the front angle as in FIG. 1 but from an upper direction, and it being understood that the claimed pattern is repeated at least vertically, as shown schematically by broken lines; and,
FIG. 3 is a sectional view along line 3-3 of FIG. 1.
The broken lines showing of a seat in FIG. 2 are for illustrative purposes only and form no part of the claimed design.