The pre-order for A Broken Lock is now available at the following retailers. It will automatically be sent to your device on May 15th when pre-ordering. If the price changes between now and then, you will automatically be charged the lowest price (with Amazon).
Amazon UK: http://www.amazon.co.uk/dp/B01DLVSNGW/
Amazon US: http://www.amazon.com/dp/B01DLVSNGW/