Hair replacement, ie wigs and hairpieces, fall under § 33 SGB V under the category "body replacement pieces"
The claim to the reimbursement of hair replacement applies except for exceptional cases only for women and children.
However, this can vary from health insurance to health insurance.
Also, the subsidy can vary from cash to cash, usually this is between 300 € to 400 € for synthetic hair and up to 915 € for real hair.
The first step for you as a patient is to get a prescription from your doctor.