The incident took place at around 7pm on Saturday 5 October at a venue inside The Cornerhouse, in Nottingham city centre.
An image of a man officers would like to speak to was issued earlier this month but he has yet to be traced.
A new image of the person has since been obtained and is being released today as part of a renewed appeal.
PC Katie Bourne, of Nottinghamshire Police, said:
“We remain very keen to speak to the man pictured in this image and are asking him, or anyone who knows him, to come forward – as we believe he will be able to assist our inquiries.
“This was an upsetting incident for the female victim and we are determined to trace the person responsible.”
Anyone with information is asked to call 101 quoting crime reference number 24*604875. Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
If you or anyone you know have been affected by the people highlighted in this article, then please report those individuals to the Police on 101 (999 if an emergency) or visit their online resources for further details of the options for reporting a crime. You can also make a report at Crimestoppers should you wish to be completely anonymous. There is help available on our support links page.