“Mr Zhang was killed in such awful circumstances, and we will not stop until we find out who did this to him.
“People needn’t be afraid to come forward with names. The DNA sample we have means that we are able to quickly and easily eliminate people from our ongoing investigation.”
The motive was thought to have been robbery, although police have not been able to confirm that.
The masked suspect in the CCTV was described as black, in his late 20s at the time, about 5ft 4ins and of an average build.
He was captured wearing a dark hat and dark clothing as he walked along Barford Street just before the murder.
The DNA sample was submitted for forensic testing, which concluded that the suspect was a man and there was a 99.99% probability that he was black.
Crimestoppers said the reward was for information given anonymously that would lead to the conviction of the person responsible for the death of Zhang, a Chinese national.