The gasket between the water pump and the plate should be the same as the gasket between the plate and the timing cover. Are you talking about the gasket between the timing cover and the block? --- That one's a timing cover gasket.
There are 3 gaskets in all: one between the timing cover and the block, and one on both sides of the water pump plate.
(Just in case, don't forget the tubes and the rubber seals that connect to the back side of the plate)
While you've got it apart, take the opportunity to set the clearance on that plate. Support the pump in a vise (by the body, not the shaft) and lay the plate on the pump with no gasket in place. Gently "work" the opening in the center of the plate with a hammer until it just barely kisses the pump impeller. When you reinstall it with the gasket in place, the clearance will be right. This operations does wonders for how well your cooling system works.