If you are simply looking for short grain Japanese rice, look out for 'sushi rice'. Although sushi rice is just standard Japanese short grain rice with added rice vinegar, many companies advertise it as sushi rice to make it easier for people to find.
For specifically Japanese style rice, brands that are big in the States are Nishiki and Kokuho Rose, both of which are also grown in California. You can also find a large variety of short grain rice at most local Asian supermarkets.
Here is a great recipe for Onigiri (Rice Balls)
• 5 cups hot cooked Japanese style short-grain rice
• 4 sheets dried nori seaweed
For the Filling
• dried bonito flakes (moistened in soy sauce)
• salted salmon grilled
• umeboshi (pickled plums)
• 2 Tbsp black sesame seeds toasted
1. Wash and cook the rice. Onigiri is made while the rice is still hot.
2. Slightly toast the nori sheets and cut sheets crosswise into 1-inch widths.
3. Toast the black sesame seeds in a dry frying pan.
4. Prepare your different fillings
- the salted salmon should be broken up into small pieces
- pit the umeboshi (pickled plums)
5. Form the triangles – When handling the hot rice, keep your hands moistened with salty water to season the rice slightly and keep it from sticking to your hands.
6. Place a handful of rice (about ½ cup) across the bent fingers of your left hand. Make an indentation in the rice and tuck in about a tsp of one of the fillings (Salmon. Plum, or Bonito flakes).
7. Use your index finger, middle finger, and thumb to mold the triangular shape.
8. Set the rice triangles down on their bases and cover each with a strip of nori seaweed.
9. Sprinkle one or both ends with the sesame seeds.