Which kind of trave agency?

Hi!
I am planning to visit China in December. According to the Chinese Embassy in Sweden I can apply for a visa directly via the Chinese Embassy in Japan but on this page it is stated that I need to apply via a travel agency. Where can I find a travel agency to do this? Can't I apply on my own since I already have plane tickets? What kind of documents do I have to bring to the embassy or the travel agency?
I am a Swedish resident and I plan to stay at a friends place in Shanghai.
Best regards,
Fanny