The ornamental design for a pitchingmachineballholder, as shown and described.
FIG. 1 is a perspective view of a pitching machine ball holder showing my new design in use;
FIG. 2 is a perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a right side view thereof, the left side view being a mirror image;
FIG. 5 is a closed end view thereof;
FIG. 6 is an open end view thereof; and,
FIG. 7 is a bottom plan view thereof.
The pitching machine, balls and hose clamps shown in broken lines in FIG. 1 denote the nature and environmental use of the design and form no part of the claimed design.