The assault happened outside Greggs in Cape Hill on Friday, November 29.
The video shows a man approaching and then shoving over the 72-year-old victim in the street, forcing him to drop the drink he was holding.
The victim suffered a back injury during the assault.
Police said it was a nasty, unprovoked attack and that the assailant was seen riding a mobility scooter. The attacker is thought to be in his 60s and is around 5ft 8ins tall, of heavy build and was wearing glasses.
Officers are asking for help to identify the offender. Anyone with information can call police on 101, quoting reference 20SW/284518Z/19.
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org