The ornamental design for a ballwheel for a wheelbarrow, as shown and described.
FIG. 1 is a top perspective view of a ball wheel for a wheelbarrow showing my new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a left side elevation view thereof, the front, rear, and right side elevation views being mirror-symmetrical thereto; and,
FIG. 4 is top plan view thereof, the bottom plan view being mirror-symmetrical thereto.
The broken lines shown in the Figures are for the purposes of illustrating portions of the ball wheel for a wheelbarrow and form no part of the claimed design. The cross-hatch indicates a contrast of appearance from the plain, adjacent surfaces.