Ahi poke craving!
This is going to sound kind of silly, but have you tried the California hotel? They cater very strongly to vacationing Hawaiians, enough so that Hawaiians have dubbed Vegas the Ninth Island. I can't vouch for the quality, but I would imagine at least the Aloha Specialties restaurant on the second floor would have poke good enough to satisfy Hawaiians. It wouldn't surprise me if their 24-hour coffee shop has it too. As a side note, if you're downtown late at night, the oxtail soup in the Cal's 24-hour coffee shop is pretty darn tasty.