From the Super Mario Wiki
Harry's Shop is located in the southwestern part of Toad Town in Paper Mario. It is a shop run by Harry T. It can be accessed when the wooden planks blocking the southern entrance of the eastern plaza are cleared, when the player completes Chapter 1.
In Chapter 4, Shy Guys run rampant throughout Toad Town with the shop's Storeroom Key being stolen by them. After retrieving the key from Shy Guy's Toy Box and returning it to Harry, as thanks, he unlocks the door to the storeroom and grants Mario access there to collect any items he pleases (Mario can also unlock the door himself, much to Harry's annoyance).
Best selling prices
The following items can be found in the storeroom. The Toy Train is required for the storyline to progress.
Names in other languages