The ornamental design for a headband or neckband, as shown and described.
FIG. 1 is a front elevation view of the headband or neckband shown as being worn as a headband;
FIG. 2 is a right side elevation view of the headband or neckband of FIG. 1;
FIG. 3 is a left side elevation view of the headband or neckband of FIGS. 1 and 2;
FIG. 4 is a rear elevation view of the headband or neckband of FIGS. 1-3;
FIG. 5 is another rear elevation view of the headband or neckband of FIGS. 1-4, as worn with the fringe element facing to the rear;
FIG. 6 is another front elevation view of the headband or neckband of FIGS. 1-5 with the fringe element facing a left side, with a right side positioning being a mirror image thereof; and,
FIG. 7 is a front elevation view of the headband or neckband of FIGS. 1-6 shown being worn as a neckband.
The dashed lines show environmental subject matter that is provided to better illustrate how the claimed design may appear when worn and that forms no part of the claimed design.