This is the style I have from Wallmart, very good price but on line it does not look like anything small enough, however right now Wallmart is putting out their spring stuff for pets, it's a free standing display somewhere near their pet department and they have this type of vest in pretty colors in very small sizes, I saw it at mine a week or so ago. but go quick all the very small pet stuff sells out quickly. They also had cute leashes, beds, sundresses and bathing suits for cheap prices and cute colors. Good luck, hope you find what you are looking for.
SimplyDog Mesh Dog Body Harness, Navy, Multiple Sizes Available: Dogs : Walmart.com