A suspect who jammed the locks of more than 20 chain stores may have used a chip carton to conceal filler used in the attacks, say police.
A CCTV image of the man in an Aberystwyth shop doorway early on 20 December - so-called 'mad Friday' - has been released by Dyfed-Powys Police.
Among those targeted in the Ceredigion town centre and in nearby retail parks were Waterstones, Halfords and Boots.
Storekeepers were also left leaflets which read: "Save our small shops".
Some shop owners said activists used putty or a car body filler, which was left to harden overnight.
The CCTV image shows a man in the doorway of sports shop in Great Darkgate Street on 20 December at 0353 GMT.
Local newspaper
Police said it appeared the man used a chip carton to conceal the substance.
Detective Inspector Greg Williams said: "A number of commercial premises were targeted in Aberystwyth on Friday night or in the early hours of Saturday morning 20 December.
"The CCTV image relates to a person who the police would like to speak to in the town centre between 2.30am and 4.30am on Saturday, 20 December - after the so-called mad Friday, so there were still a lot of people around."
Det Insp Williams also asked for a woman to come forward who delivered a note to the local newspaper, the Cambrian News, which revealed details of the attack.
Following the incident, one shop manager had to smash a window to gain access to his premises on a retail park, while another was forced to change her town centre store's locks.
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