I don't know the size, but these guys will have the hardware once you find the size:
What Audiomax said. When you need help with hardware, visit a hardware store: Home Depot, Lowes, Ace, True Value, etc.
Once you've identified the thread pitch X length they'll probably have a choice of materials. You can feed your audiophilia nervosa for about $3. ;-)
P.S. to avoid scratching your tonearm mounting plate, pick up some washers too.