Yellowfin tuna steak is widely available. Local fish mongers, seafood markets, and Japanese grocery stores (e.g. Nijiya, Mitsuwa, and Marukai) commonly carry yellowfin tuna. You can also find yellowfin tuna at high-end markets like Whole Foods or small specialty grocers. The other ingredients for this dish can be found at your local grocery store or the Japanese grocery stores listed above.