List of shops in Paper Mario: The Thousand-Year Door
From the Super Mario Wiki
Constantly found in Paper Mario: The Thousand-Year Door, Item and Badge shops and their variations will sell different items and badges to Mario. Almost all of the shops are found in major cities of the Mushroom Kingdom, such as Petalburg or Twilight Town. The player earns one shop point for every purchase. When a certain amount of shop points is earned, the player receives a free gift.
Once Mario earns 300 shop points and is given the Gold Bar ×3, the point system rests to zero and he can accumulate points all over again.
For a complete listing of prices of how much Mario can sell items for, see: List of selling prices in Paper Mario: The Thousand-Year Door