The ornamental design for a vehicleholster mount, as shown and described.
FIG. 1 is a perspective view of the vehicle holster mount positioned in an exemplary installation below an exemplary steering column (shown in phantom and not part of the claimed invention);
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a side view thereof; and,
FIG. 5 is rear view thereof also showing an exemplary holster and handgun (in phantom and not a part of the claimed invention) being held by the vehicle holster mount.