Sony RX10 IV camera is only available at Amazon for pre-order. The camera is already available at B&H Store, check here.
Sony RX10 4 camera is one of the best camera ever made by Sony the camera feature same as sensor as used inside the Sony RX100 V camera. not only that the camera features world fastest autofocusing is speed of 0.03 second despite of having a 25 x optical zoom lens.
you can look at the specifications comparison here