My roommate got a hide-a-squirrel for his Yorkie/Maltese (She's 10-12lbs) from Petsmart. I found one at a local petstore called Wylie Wagg (they have an online store as well) in my area and it was much smaller than the one my roommate got which was perfect for my 4lbs Yorkie and his small mouth. He loves it! I paid $10 for mine and I'm so glad I got it.
Here's the site's link:
Hide-A-Squirrel
I got the junior one.