you can preorder a signed copy from Porter Square Books. They will ship anywhere in the U.S. If you're local you have the option of picking it up in-store. Unfortunately they cannot ship internationally, but Porter Square Books is the only independent bookstore offering pre-orders of signed copies.
This is a really wonderful thing Gaiman is doing for the store. If you're interested in the book and would like a signed copy, please consider buying it from Porter Square Books!
They will ship on the release date, currently June 18.