I have co-workers that buy cars all the time. One of the best places they buy from is Wal-mart. Not just random off the street shopping. Sometimes they show up as the boxes are being opened, as the shelves are being stocked. This why they get the first pick of the inventory. They get to meet the sales rep and find out about Hotwheels inside news.

Also try hobby stores that sell trains, remote control cars, D&D and miniatures. They sometimes carry Hotwheels that are rare and untapped.

Happy hunting.