When we were in Tokorozawa we took the time to supply some pre-washed rice and water. The prices are one level lower in Tokorozawa compared to Tokyo so we get more for the money, which is good.
On our way back to Tokyo we stopped by Ishihara-san’s place to leave the rice and water there, until the next trip to the Tohoku area. You can find the details at the Tohoku Donation page.