WiFi controlled 240V adapter

You can make one yourself. Buy a properly current rated 240V AC relay that uses a control voltage of 120V AC and then wire the 120V AC into a Smart Outlet controller or other similar smart controller. So when you trigger the smart controller to turn on it closes the input voltage to the relay thus providing 120V AC which then closes the 240V AC side of the relay and provides the voltage to the amplifier. Before doing this you will want to confirm that the amplifier your going to control will return to the power on state if the supply voltage is removed and then provide again. A rough price to build this yourself including relay, enclosure and smart controller is around $60-$80 USD if you need to buy everything.

Be careful switching 240V devices with the DLI 240V switch, I'm not sure if they redid their design but the earlier 240V units only switched one of the two hot AC line going to the device plugged into it, so basically when the outlet is OFF you still have 120V to ground on the UNSWITCHED Leg of the Power switch going to the 240V device.