You can get those exact set screws from any True Value, and most likely the warehouse stores as well.
But yeah,
if you can wait see if Konig will priority mail them to you.
I bought extras from True Value, but I don't have the part number any more.
*Be sure to check the boxes/plastic bags they put the wheels in, since some of mine fell out of the little bubble wrap envelopes they put the center caps/stickers, set screws and allen keys in.