I claim the ornamental design for a flag football belt/waistband clip, as shown and described.
FIG. 1 is a front and left side per perspective view of the flag football belt/waistband clip shown in place on a belt and having a flag attached thereto;
FIG. 2 is a top left side and perspective view of the flag football belt/waistband clip;
FIG. 3 is a right side elevation view of the flag football belt/waistband clip;
FIG. 4 is a left side elevation view of the flag football belt/waistband clip;
FIG. 5 is a front view of the flag football belt/waistband clip;
FIG. 6 is a bottom view of the flag football belt/waistband clip;
FIG. 7 is a top plan view of the flag football belt/waistband clip; and,
FIG. 8 is a rear view of the flag football belt/waistband clip.
The broken lines in FIG. 1 of the drawings show unclaimed environment only and form no part of the claimed design.