Aw! I'm so excited for your puppy to come home.
I've seen some pretty teeny doggy collars. I know Jackson, my 15lb'er is 11" around his neck (collar size is usually 10-14") and he wears the 3/4" width or 5/8" width ones so I'd imagine a little one would be pretty small.
Have you checked out etsy.com? A ton of really good sellers who make great personalized things and I'm sure someone would be willing to make a small collar!