Right here on this website.
http://castboolits.gunloads.com/showthread.php?213750-Stainless-Steel-Media-Pellet-Pins-for-wet-tumbling-62x255-(these-are-the-better-ones
He'll sell you less than the 5-pound quantity most folks get; I bought 2 pounds and they're plenty to fill up both drums of the HF tumbler.