The stock knob ES/P5 knob and anything with same threads will fit. I got the aftermarket Madzaspeed one from Corksport. It's leather, nicely-weighted and goes well with the B&M shifter. I love it and it has perforations which match the e-brake handle and steering wheel. Check the Corksport website for more info.
Thanks for the replies. I want to try and match the interior of the car. I have the tan interior and polished Daveb rings, the radio is also chrome along with the door handles. I think I want a chrome one but can't find anything but a round ball.