Kurt is the Pokémon breeder who lives in Azalea Town and is a skilled craftsman who makes Poké Balls. He is known for making special Poké Balls, but he doesn't give away the GS Ball.
Here's what you need to do to get the GS Ball:
1. Talk to Kurt: He will tell you about a special Poké Ball that needs a special kind of Apricorn to make.
2. Find the Apricorn: The Apricorn you need is a Silver Apricorn, found in the Ilex Forest in the northeast corner of the Johto region.
3. Give the Apricorn to Kurt: He will use the Silver Apricorn to make the GS Ball for you.
Let me know if you have any other questions about Pokémon Gold, Silver, or Crystal!