I’m pretty sure the Bluetooth module in a TR will be USB. It was USB on my UK Z1 which had internal bluetooth.
Can someone with a UK or Japanese model of the TR with bluetooth just check in their device manager and see what it says in the bluetooth section?
I’m sure on the Z1 off the top of my memory it was something like USB Bluetooth Sony Model number or something like that.
It’s just a matter of finding where it is connected on the inside and then modifying a USB dongle to fit in, wouldn’t have to be a Sony one.