Where and when does Holden get the red hunting hat?

You can find the answer to this question right at the
start of Chapter 3.  It's about one page into that chapter (page 17 in my copy of the
book).

Holden Caulfield gets the red hunting hat while he
is in New York City on the day that the novel starts (this is when he is in with the
fencing team and loses all their stuff).  Right after he loses the swords, they get out
of the subway and he sees the hat in the window of a sporting goods
store.

He likes it and buys it for one
dollar.