I claim the ornamental design for a promotional cap strap cover, as shown and described.
FIG. 1 is a perspective view of a promotional cap strap cover showing the top, back, and right end of the claimed design;
FIG. 2 is a top plan view of the promotional cap strap cover, the bottom plan view being a mirror image thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a back elevation view thereof;
FIG. 5 is a right end elevation view thereof, the left end elevation view being a mirror image thereof; and,
FIG. 6 is a perspective view of the promotional cap strap cover as shown mounted to on the back strap of a cap.
The broken lines along the surfaces of the promotional cap strap cover depict environmental structure for the purposes of illustrating placement of promotional marking on the promotional cap strap cover and form no part of the claimed design. The broken line outline of the cap in the view of FIG. 6 illustrates the environment of the promotional cap strap cover and forms no part of the claimed design.