You might do a search but I have found them on Amazon or Ebay. Not always available though. If you can find the type that have a short starter built in they are worth the extra $$ IMO.
I can make you some up up. How many shots and what shape and quantity (within reason) would you like them to be. If you want a counterbore in them to align the ball let be know the distance of the flats. I can make them and send them to you at no charge, it's the giving time of the year. Oak, pecan, mesquite,cherry,walnut, sycamore, hickory are the hardwoods I have on hand.