How much is the visa going to mainland for re-applying?

Justine, you can try to apply for a single entry one in HK after you go to HK. But if you cannot get it, you can find a travel agency to get it for you. Here is the contact number of the office of the commissioner of the ministry of foreign affairs of PRC in HK: (852)-34132300. You can contact with the office and know about the relevant information.