Tourist Visas for HK required by a NIGERIAN Citizen

Hi I am a NIGERIAN living both in the UK (resident Permit) and Nigeria. I would like to visit Hongkong as a Tourist. I gather Nigerians must obtain Entry permits before entering. Does anyone know how much will the tourist type cost - and whether the Cashiers cheque or postal order has to be submitted with the original application papers. By the way I could not figure out the cost.