Remember that it's metric - a typical hardware store may not have it unless they have a good selection of "special fasteners".I don't know the size but a good hardware store (True Value or Ace) should have an assortment of different ones to try out. Just take the knob with you and have at it!
The set screw that holds the gear shift knob in place (well, keeps it from rotating) fell out & was lost to a vacuum cleaner.
Any idea what size it is & where I can get a new one?