The ornamental design for a rear bottomflap for baby bodysuit, as shown and described.
FIG. 1 is a front view of the rear bottom flap for a baby bodysuit;
FIG. 2 is a rear view thereof, of the rear bottom flap for a baby bodysuit, shown in the closed position;
FIG. 3 is a side view thereof, of the rear bottom flap for a baby bodysuit, shown in the closed position; and,
FIG. 4 is another rear view of the rear bottom flap for a baby bodysuit shown in the open position.
The broken lines shown in the various views are included for illustrating environmental structures, and are unclaimed subject matter, forming no part of the claimed design for the rear bottom flap for a baby bodysuit.