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New fluid can quieten a noisy pump ;) check that there isn't any play at the pulley end.
Can you get gasket paper? Have made gaskets for oil areas from cereal packets soaked in oil. But not sure that would work on a water pump. Have used a thin bead of rtv silicone, from a medical syringe, on a cereal packet as an emergency gasket that lasted till I sold the car.
Sure it is a gasket not an o ring?
Get a water pump that comes with a gasket. Some do some don't.
What micra is it?
Read forward...K11. Has it got fluid power steering?