Rice
Here is a list of known rice vendors. Whether or not the rice is specialized for making sake (ex.- Yamada Nishiki) or food rice that can be used for sake making, the rice still must be polished much more than food rice. This calls for a specialized mill. And that greatly limits the number of vendors outside of Japan.
Minnesota Rice and Milling
Offers a variety of rice types for sake brewing including Yamada Nishiki and Calrose.
Valley Select
“For decades, California rice varieties have been used by Japanese sake breweries in the United States to produce high quality sake brewed in the US for the US and export markets.
In 2012, Valley Select noticed a need for more high quality sake rice to serve sake breweries here in the US. Valley Select invested in state of the art, Japanese equipment, designed specifically to mill rice for the highest quality, Dai Ginjo sake.”