If you still looking for the answer... If you are staying at Shamian Island you could try Maria the "Romantic consultant", she stands on the corner vis-a-vis White Swan. She will provide the girls, did not try her service, so cant say aynthing about quality or price.
Other tips could be check outside your hotel in the evening. Good chance it will be some hanging around there.
Other tips could be check outside your hotel in the evening. Good chance it will be some hanging around there.