I am US citizen with Residency Permit in Hungary. Need to go to Canton Fair + potential suppliers

I am a US citizen with a Residency/Work permit in Hungary. I am a Country Manager (Director) for a Hungarian company and would like to visit China in April for the Canton Fair and combine the trip with checking on potential suppliers around Ningbo on behalf of the Hungarian company . I do not have an invitation from any Chinese companies and do not have anyone in China to invite me. Is an invitation from China necessary? Can I apply for a visa to China in Hungary? Should it be a business or a tourist? Can I provide airline ticket and hotel reservations instead of an invitation? When should I apply for it if I need to be there for Canton Fair on April 15, 2014. If I am flying through Hong Kong, is that I can apply and get in Hong Kong.
Thank you in advance,
Natalia Nicol