Police were called at approximately 7.30pm on Tuesday, 17 October after a firework was let off inside a shop on Churchfields Road, injuring a five year old child.
The child was hit in the stomach, sustaining minor injuries but did not require hospital treatment.
The suspect is described as a white male, wearing a white short sleeved t-shirt and a black cap or balaclava.
Bromley police are currently investigating and no arrests have yet been made.
Anyone with information should contact 101 or call Crimestoppers on 0800 555 111.