From what I've heard (note that heard: I have no experience in this), the sushi bar is generally not open during lunch (or is still doing coffee/pastries) and thus will not be served.
However, if you ask around Kona Cafe (or at the bar), they may have someone on hand who can make it. They may not. It's up to chance and the wheel of the dice. The later your lunch, the more likely the sushi is open: I believe they open actually a bit before Kona switches from lunch to dinner. But it all depends. Just cross your fingers, I guess.