Those probably come with the "official" Microsizers carrying case.
There are sticker creation kits that allow you to make your own. You could use the back of the packaging for the cars and accessories with these kits. Just cut out the little icon off the package that you want to be the sticker, then place it between the sheets of the sticker kits, cut around it and you've got a sticker.
Or you could just glue the cut out straight onto whatever.
Maybe someone can help you more, just offering some alternatives.
