Always best to buy directly from the author/artist. But almost as good is to pop into your local book and gift shop to support the indies.

You can get some of the books and cards in these stores: 

Printed Matter (New York)

Motto (Berlin)

Utrecht (Tokyo)

Le Bal (Paris)

Ti Pi Tin (London)

Brunswick East Coffee (London)

Skylight Books (Los Angeles)

some stuff is also on Amazon UK

and Amazon US

please get in touch if you'd like to stock any of the titles.