The girl was delivering newspapers in the village of Lanchester, Durham, when she was attacked at 8am on 19 December.
Police said a reward offered for an arrest and conviction had risen to pounds 14,000, after a large donation by Sir Tom Cowie, a millionaire car dealer who has eight daughters, who lives near the village. Police have stopped cars and spoken to pedestrians and other road users in the village in an attempt to build up a picture of the attack.
Detective Chief Inspector Max Currah, leading the inquiry, said: 'It is imperative that I speak to a man seen in the area wearing a dark tracksuit with a peppermint- green stripe. He was seen by the victim near the vicarage in Cadger Bank, seconds before the attack.'
The man is described as aged between 17 and his early 20s, and about 5ft 9in tall. He was of normal to thin build with black or brown straight hair.
Mr Currah said he was anxious to talk to any joggers or anyone who was wearing a tracksuit in or around the village on the morning of the attack. A villager reported seeing a man with a green striped tracksuit and similar looks in the area a week before, at the same time in the morning. The same witness said moments later he spotted the papergirl. Mr Currah said he was sure that the rapist was a local man.