https://www.amazon.com/dp/B00CHSVVWO/ref=sspa_mw_detail_0?psc=1&th=1

I got this for my Boston a few months ago, and so far it has worked very well. I like that it fastens on the top-it seems to make it a lot easier to get him into it that way. He is around 20 lbs, and I got him a large.