This is one of three kits sold in 2002 that aren't new sets but is a collection of previously sold Harry Potter LEGO® sets. I am guessing that Lego did this so that people who wanted multiple sets could get them in one purchase, but I don't think they were all that popular because they only did this for a few years.
I have never seen this kit listed on either Amazon or eBay but I've included links to both sources just in case you get lucky. However, it will be much easier for you to buy the sets that were included in this kit separately, which is why I've included links to each set in the description.
Looking for more Harry Potter LEGO® sets? You can see the list of all the sets here.
Do you live outside the United States?
Although some items on Amazon can be shipped world wide, you will probably have the best luck with eBay and Etsy. Click here to see how to know if an item from those three sites can be shipped outside the U.S.A., as well as how you can buy items found and have them shipped to you even if the store you buy from doesn't ship to your country.(Clicking this will open a new window so you won't lose the page you are currently on.)
This LEGO® set contains small pieces that could be a choke hazard and is not meant for children age three and younger. LEGO® is a trademark of the LEGO Group of companies which does not sponsor, authorize or endorse this site.