Available at all good bookstores, but here are a few to try...

Online (free NZ shipping)
Five Dogs Books 

Online (international shipping)

Paper Plus // Whitcoulls

Auckland Unity Books Auckland // The Women's Bookshop // Time Out Bookstore // Poppies Remuera // The Book Lover // Dear Reader // University Bookshop // Paradox

Tauranga Books a Plenty // Rotorua McLeod's Booksellers // New Plymouth Beattie & Forbes // Havelock North Poppies // Palmerston North Bruce McKenzie Booksellers // Masterton Hedley's Bookshop

 Wellington Unity Books Wellington // Vic Books // Marsden Books // Millwood Gallery //

Nelson Page & Blackmore // Christchurch Scorpio Books // University Bookshop //  Picadilly Bookshop // Dunedin University Bookshop