Link above is for a 2-1/4" diameter knob. Big, prob same you currently have.
Hurst sells the one that comes with the Billet shifter. It's smaller, 1-3/4" diameter...
http://www.hurst-shifters.com/hurst-...KNOB-6-SPEED_2
Not 100% sure it will fit the stock stick though. Like mentioned, If I were you I'd get an aftermarket shifter... Hurst Billet... Pro 5.0. You wont be disappointed.