If you don't mind ordering online, there's a whole list of online parts dealers in the resources section of this website (called "recommended moped shops" i think). Either that, or with the cable you've got, it sound like it's just too long and there's too much slack in it, causing it to not open the throttle all the way. Put a spacer between the cable's tube and the cable tube attached to the carb (basically making the cable tube longer). But if you want to order over the internet, I always go with www.themopedjunkyard.com because they can have the part at your front door in less than a week.