Pakistani Citizen US permanent resident trying to apply for Mainland China Visa

I'm going to be studying in Hong Kong for a semester starting in January. I have been trying to get a multiple entry tourist visa in the US so that I can go visit Mainland China while I am studying in Hong Kong. I sent my visa to a travel agency and they told me that I would have to go to the Embassy in person in order to apply for my visa (I would have to catch a 3-hour flight in order to get to the nearest embassy.) Is there no way I could apply for a visa to China while I am in Hong Kong?