Rowling's 65 publishers in more than 200 territories will distribute a poster of Madeleine, who has been missing for more than two months, to stores elling "Harry Potter and the Deathly Hallows," public relations firm Colman Getty said today.
The book, the seventh and final installment in the schoolboy wizard's adventures, goes on sale Saturday.
In a statement, Rowling said she was asking stores to display the poster, which will include the Web address of the International Centre for Missing and Exploited Children.
"I fervently hope that posters displayed prominently in shops all over the world when the new book comes out will help find Madeleine McCann and will raise the profile of the many other missing children in different countries," Rowling said.
Madeleine, 4, disappeared on May 3 after her parents left her and her 2-year-old twin siblings alone in their room while they went to a restaurant inside their hotel complex in Praia da Luz, a resort town in Portugal's Algarve region.
Rowling has pledged several hundred thousand dollars to a reward for Madeleine's safe return.