This book is simply called "Sonic the Hedgehog". (Makes it kind of hard to look up / find) and is yet ANOTHER faked-up "origin story" for Sonic, from back when nobody knew much and just made up anything. The book is made by Watermill Press, and written by Judy Nayer…
Here is a Pajama/PJ top with a nice modern design. It uses silvertone ink for a starburst behind jumping Sonic. This may have been released in more than just Australia.