The Raspberry Pi Zero was released over two months ago, but it's still incredibly hard to find. Where Is My Pi Zero? is a simple site that will check stock for you at a number of retailers. Where Is My Pi Zero checks stock at the Raspberry Pi Swag Store, Pimoroni, The Pi Hut, Adafruit and Element14. They're all currently out of stock, but it's a good site to keep an eye on if you're looking to order one any time soon. Just remember to factor in shipping as well.