Stop fighting it. Today is Cyber Monday. The day that employees come back to work after Thanksgiving and get even more shopping done. While Black Friday is a crowded, social and sometimes spontaneous sport, Cyber Monday is a solitary and targeted shopping strike.
On Sundays, your employees looked at their shopping lists and compared them to what they really purchased (intentionally or impulsively or because what they really wanted was no longer there). Today is about sifting through their emails and filling in the wholes to shop online.
Stop fighting it. They will shop today anyways. I recommend that in addition to lunch hour today there should be the Cyber hour. Have everyone pull out the list of all the things they need and go shop for an hour. Perhaps other employees could shout out good deals they found or coupon codes. Turst me. This is a good thing. It will make for productive employees the rest of the day!