The ornamental design for a mounting bracketassembly of tow mirror, as shown and described.
FIG. 1 is a perspective view of a mounting bracket assembly of tow mirror showing my new design;
FIG. 2 is a front view of the design;
FIG. 3 is a rear view of the design;
FIG. 4 is a left side view of the design;
FIG. 5 is a right side view of the design;
FIG. 6 is a top view of the design; and
FIG. 7 is a bottom view of the design; and,
FIG. 8 is a perspective view showing mounting bracket assembly of tow mirror and a tow mirror shown in dotted line, for illustrative purpose only not forming part of the claimed design.