There are two in the airport at HKG that will get you also multi-entry visa for China. It usually takes around 6 hours, so if you get an am arrival, you can fly (or take the train) to China in the late afternoon. I did once get stuck where they could not get it for me until the next morning- so make sure you have a flexible ticket if flying same day out of HKG. For some reason, they always have asked for a business card as well- a colleague of mine didn't have one so they printed one for him (it seemed strange to me- but they said if you want the one year visa that is the rule).