As of January 2014, Search Inside Yourself is published in English and 12 other languages. Here is the entire set, including the 5 English-language editions (the US hardcover edition, 2 UK editions and 2 international editions).
Collect the whole set!
Update (2014/01/27): Cathy from HarperCollins says, “SIY has been licensed to 24 foreign publishers so far – you should have a few more editions to add to the collection soon!”