I have built in a "UGREEN V4.1 Wireless Bluetooth Receiver Audio Adapter with 3.5mm and 2 RCA Port".
Power is supplied by a TO220 7805.
Fortunately the device is always visible after power on, so push button not necessary to be used.
I have connected it to tuner input because we do not use it any more and actually bluetooth is a kind of radio signal.
Pictures
