That's a toughie. In the electonics industry we call it a "tweeker"
In manuals it's described as a ------- adjustment tool ( potentiometer adjustment tool, Variable capacitor adjustment tool,...etc...) If you don't need nylon or plastic, an inexpensive jewelers' screwdriver will do. At Sears in the 99 cent bin.
Or walk into an electronics store and ask for "that plastic thing for adjusting small components- kinda like a long plastic thing with a tiny screwdriver on the end"
Or scrape the rubber off the end of a bobby pin
Or get one of the rods they use for plastic welding and scrape the end into a screwdriver.
If all else fails, ask a friend in the biz if he/she has an extra?