It is everywhere, aliexpress, banggood or ebay, in fact just ordered another one as I’m running out of them BT201 Dual Mode 5.0 Bluetooth Lossless Audio Power Amplifier Board Module TF Card U Disk Ble Spp Serial Port Transparent 5V DC Sale - Banggood UK Mobile-arrival notice
The sound quality is very good, and there is plenty of documentation on the web to describe AT commands, but it works just as well with buttons out of the box. My favourite feature is you can set your own bluetooth name.