Yes, most rice cookers have timers on them and it usually takes about an hour to cook the rice. If you steam the fish along with the rice, they will both be cooked.
You can't hook them both up at the same time unless you buy a separate adapter. Try going to an electronics store, and asking the employees what they have.
The most handy option would be a piece of sheet metal however tall you'd like; I would recommend at least 8" tall by 20" long. Then, I would bend the...