Shimano XT M-737 left side shifter/brake combination. Trigger version, 3 speed for front derailleur. $30.
Shimano LX M-570 best side shifter. Trigger variation, 9 speed for rear derailleur. $25.
Shimano XT M-739 right side shifter. Trigger variation, 8 speed for rear derailleur. $20.
SRAM SRT600-71 ideal side shifter. Grip twist version, 7 speed for rear derailleur. $15.