Any "normal" working BT headset works. I've tried official Sony, Jabra, Motorola and Plantronics with no issues. The official Sony is the best one, but if you can't get a deal on one just use any BT you find.
Most BT headsets can be programmed for multiple devices, so if you have one for your cellphone, you can use that same one without losing any settings or reprogramming it back and forth.