Which visa

Hi please advise which type of entry permit can one apply for when visiting China to purchase bulks of virgin unprocessed hair. what exactly is needed in the visitation? does the embassy require both the invitee's chinese identity document and a copy of their passport? Does one need to submit a 3 months bank statement or a 6 months bank statement? I have been to PRC before but it was for a group seminar and stayed in Beijing and also travelled to Guangzhou. Is the official stamp compulsory