The incident took place near the railway bridge over the River Clyde on the evening of Monday, July 16.
Officers want to speak to two men who are seen on CCTV in the area who may have information that can assist enquiries.
The first man is described as white, mid-20s to mid-30s, 5ft 8, of medium build and had brown hair in a side parting. He was wearing a dark coloured zip-up jacket, dark coloured trousers and shoes and was carrying a black rucksack over his shoulders.
The second man who is seen nearby, is described as having sallow skin, is of medium build, and was wearing a light coloured zip up hooded top with white logo at left breast area and a dark coloured skip cap with a light coloured logo.
Detective Inspector David MacGregor, Divisional Rape Investigation Unit, said: “This was a traumatic attack for this woman and it is critical that we trace the person responsible as soon as possible.
“I would like to reassure the community that our officers are doing everything they can, including an extensive review of CCTV in the area, however, we need help from members of the public who may have vital information to assist with the investigation and therefore we are appealing for these two men to come forward”
“The first man is seen helping the 30 year-old woman shortly after the attack and had walked her to the Riverboat Casino. The second man is seen nearby, and may have witnessed the attack or have information that can help us.
“I would urge these men to come forward.”
Anyone with information is urged to contact officers on 101.