The ornamental design for a strapoverlay for an article of headwear, as shown and described.
FIG. 1 is a perspective view of a strap overlay for an article of headwear.
FIG. 2 is a front view thereof.
FIG. 3 is a back view thereof, with a fabric adhered thereto.
FIG. 4 is a right side view thereof.
FIG. 5 is a left side view thereof.
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines outside of the claimed boundary form the environmental structure of the strap overlay for article of headwear which forms no part of the claimed design. The broken lines shown inside of the claimed boundary illustrate an exemplary printed design on the strap overlay for article of headwear that forms no part of the claimed design.