We claim the ornamental design for the handrail support member, as shown and described.
FIG. 1 is a top perspective view of the handrail support member;
FIG. 2 is a bottom perspective view of FIG. 1;
FIG. 3 is a left side view of FIG. 1;
FIG. 4 is a right side view of FIG. 1;
FIG. 5 is a front view of FIG. 1;
FIG. 6 is a rear view of FIG. 1;
FIG. 7 is a top view of FIG. 1; and,
FIG. 8 is a bottom view of FIG. 1.
The broken lines shown in FIGS. 1-2 and FIGS. 5-8 illustrate portions of the handrail support member and form no part of the claimed design. The handrail support member is shown with a symbolic break in its length. The appearance of any portion of the article between the broken lines forms no part of the claimed design.