Green sequin ears with red sequin bow are traditionally available at WDW and DLR during the holidays but do indeed sell out quickly. Our red ones came from the UK. Not sure when the last time it was they were available in parks here.
Watch
Disneystore.com. They have Halloween ones right now but will have Christmas ones later. But they won't last long.
IMG_1594 by
mom2rtk, on Flickr