The ornamental design for a stringinstrumentbowgrip, as shown and described.
FIG. 1 is a front view of a string instrument bow grip showing my new design; the broken lines showing portions of a hand and string instrument bow are for illustrative purposes only and form no part of the claimed design;
FIG. 2 is top view of my new design shown in FIG. 1.
FIG. 3 is a front view of FIG. 1.
FIG. 4 is a bottom view of FIG. 1.
FIG. 5 is a left side elevational view of the new design shown in FIG. 1; and,
FIG. 6 is a right side elevational view of the new design shown in FIG. 1.