Hello Kitty New Era 59fifty

how to shrink a fitted hat?

today i bought a fitted hat .

http://www.eblens.com/blog/wp-content/uploads/2010/08/hello-kitty-new-era-59fifty-fitted-cap.002.jpg

and its size 7 .
its a little loose on me and goes over my ears by a little.
how can i shrink it safely without messing it up?

pt lining inside of the little tab parts

Unboxing: Hello Kitty New Era (Black & Yellow)