You can buy it from a range of apparels by click onto the images of 'American Psycho' and it will take you to the store website or click on one of these online store of your choice:
Click for larger images
I can't wait to finally launch my new side project this year: The Black Imp.
Their online store via Society6 will be coming in the near future. The illustrations will be displayed on their Instagram and Tumblr sites soon.