I can find short-grain rice easily enough. What I'm looking for is cheap and easily-available things to fill them with. There's room for about one TBS filling in a half-cup mold. My carrot, cucumber, and cream cheese filling works better as a rolled sushi.
I'm real-food centric, and would rather avoid a canned product. I can do roast chicken very occasionally, but would prefer cheese if I'm using a protein in them.