Enter any of the main areas of the city of Freeport (e.g., North, West, East, or South).
Within 30 minutes, find a set of acid-filled test tubes (they look like 5 vials of purple liquid standing in a small, wooden rack). I found mine in West Freeport in the pet store.
Use the acid to destroy 5 shipments of tin (they look like rectangular, dark wood boxes with peaked lids , found near merchants). You may need to enter all areas of Freeport to find enough. Again in West Freeport, just outside the pet store was one. Another was at the end of the row of merchants there. There was a third one along the road to the inn in West Freeport. I found a 4th in North Freeport. (Go back through the sewers to get there.) And I was in West Freeport again with about 13 minutes and noticed that the box in front of the pet store had respawned. Making 5. Then I jumped into the pit in West Freeport to get to the revive point in commonlands for a short trip to Gil in the tower.