The ornamental design for a weight for vibrationmotor, as shown and described.
FIG. 1 is a perspective view of the front, right and top of a weight for vibration motor showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a right side view, left side view being a mirror image thereof; and,
FIG. 7 is a reference view thereof, where the broken lines showing portions of the weight for vibration motor is included for illustrating environmental structure and forms no part of the claimed design.