Standard YZ from 83 onwards are available (in parts) from Yamaha. Tidy unit, easy to get spare tubes, side pull, sano appearance and cheap. YZ80 and IT175,200,250,490 for 1/4 turn action and YZ125 Up for a more progressive ratio. They usually sell on Ebay complete for about $20 used, get a new tube in plastic or billet if you prefer for another $20 odd and you have a reliable throttle solution for most applications.
Option options
The throttle tube and Housing sizes are different for the 1/4 turn and 1/2 ish turn styles, so make sure you get all the components to match the assembly you desire. Look the same but are not, so a bigger YZ tube will not work with the smaller YZ80 and IT style unit.