That bike uses the standard SRAM grip shifter you can find anywhere.
http://www.amazon.com/s/qid=1246935221/ref=sr_nr_p_4_1?ie=UTF8&rs=3494311&bbn=3494311&rnid=219891011&rh=n%3A3375251%2Cn%3A%213375301%2Cn%3A3403201%2Cn%3A3404731%2Cn%3A3494311%2Cp%5F4%3ASram