No problem, you can still make this dish! We are lucky to have access to great sashimi in Hawaii (in Honolulu we usually visit Tamashiro Market), but know that it's not always easy to find sashimi. For last minute meals, you can always use canned tuna or imitation crab (just mix with a bit of mayo like we do in these Tuna Rice Bowls), and use that in place of the sashimi. If you have a big group and some people might not like raw fish, you can offer both sashimi and the canned tuna at the table. Let everyone choose which they want to use for their own sushi.