Georgina Meier, 30, disappeared on March 25 from her home in Honeypot Lane, Stanmore, and despite several police appeals, she has not been traced.
Ms Meier wears a Hare Krishna dress and face markings, she was last seen wearing a green sari, and she has recently shaved her head bald leaving just a ponytail.
Police have said the 5ft 4inches tall white woman may have a sunburnt face, she usually has a bright green budgie in a holdall with her, and could be pushing her possessions round in a trolley.
Officers first appealed through the media at the start of this month, prompting sightings of Ms Meier in Covent Garden yesterday evening and also at the Hare Krishna Temple in Tottenham Court Road.
However, police have been unable to find her as she left the temple when the receptionist said she was going to call an associate.
Police say they are extremely concerned for her safety, and that she may be unwell and in need of hospital treatment.
Anyone with information can contact Harrow Police on 0208 733 4335, or call Missing People 0500 700 700.