The government owns military fighter jets, and international laws prohibit the sale of the aircraft to individuals. Military contractors can operate fighter jets but international arms regulations prohibit the sale of operational military planes to private entities.
Private companies are not allowed to use private fighter jets for operational purposes involving weapons. The other issue is the international regulations also prohibit that modification of aircraft with a civil design for military operations. Any such aircraft modified in disguise would not be able to get registered so you cannot fly it.