Tell us why you think, or how you know the needle seat is needing replacement? If its the press fit type, I don't believe they are available. it came as part of the carb body.
Its a brass part that won't see wear as the float valves are rubber tipped. They seldom fail if it uses the rubber tipped float valves.
If it's corroded, clean it, add a new rubber tipped valve, and call it good.