In Los Angeles I get them from the stellar spice shop Le Sanctuaire but a word of warning as they are not cheap. Individual peppercorns are very potent and go a long way. I grind mine as needed in a coffee grinder reserved for spices and rub the powder onto steaks be it ribeye or kobe tri-tip with salt as a dry rub.
The pepper is native of the Tasmania rain forest. The plant bears black fruit, the size of a pea, containing numerous small seeds. When dried the flavor has a spicy kick that reminds one of a hot blueberry. They pepper seems to meld with the meat in a way that enhances the flavor without drawing too much attention.