Visa on arrival at HongKong airport for Czech passport holders ?

Hi, I am going to fly to Chongqing to attend an academic conference but I will stop and transit in HongKong first. I am holding an invitation letter from a University in Chongqing, can I ask for visa on arrival in Chongqing? Will I be allowed to get on board the flight from HK to Chongqing? I know I could ask for visa on arrival at HK, but I have only a couple of hours for transit? Many thanks for advice!!