Bishul Ahkum regarding rice

Question

There is a fish market local to me not owned by Jews. They exclusively sell kosher fish. They also make sushi for you on the spot. The possible problem is the rice. They cook the rice in a rice cooker and the gentile owner obviously turns on the cooker. Can I purchase sushi there? If yes, can I purchase sushi from them Erev Pesach and Hol Hamoed to eat on Pesach? Thank you, Sander Silvera