At the character screen, click Change Quest.
Under ACT II Chapter 7: Blood and Sand, select Begin Quest. Click Select Game.
Your character will spawn at the Hidden Camp. Don’t use the Waypoint. Instead, walk to the northeast entrance to the Caldeum Bazaar as shown in the mini-map below.
Locate the small water fountain to the left. Next to the water fountain you will see a small girl, who immediately says …
Squirt the Peddler: “I may look small, but I’ll hurt you if you try to steal from me.”
She’s a merchant. Click the Miscellaneous tab (with the red potion icon). At the bottom you should see the Wirt’s Bell item for 100,000 gold. (Looks like the girl is the one trying to steal from you …)
Squirt the Peddler might not have the item for sale all the time. It’s random. You might have to leave the game, and resume. Rinse and repeat until she has the Wirt’s Bell on sale.
Bonus: Once you buy the Wirt’s Bell, an achievement appears onscreen titled: “Wirt’s Case Scenario”.