It's one of the most common questions I get asked. The short answer is, 'I'm afraid I can't help. I just write the things.'

However ...

For any book that's out of print, used bookstores are your best bet. There are plenty of places online, many of which have a 'notify me when the book's available' facility. Put in the effort and you stand a good chance of tracking the books down. And don't be put off by high prices (Dragonstorm seems particularly expensive at the moment) - cheaper copies do pop up from time to time.

Good luck!