Rebelscum reader Vincent P. found the first two sets in Mattel's Hot Wheels Star Wars Character Cars two pack collection. He spotted the Han Solo & Chewbacca and C-3PO & R2-D2 sets along with the currently available single pack cars at Toys "R" Us in Singapore. Click the thumbnails above to have a closer look.
UPDATE: Based on comments on this story (and an email from Dan Y.), these two packs have turned up in Canada, the U.S., and Australia as well.