Sirius Black Question -NO DEATHLY HALLOWS SPOILERS?

I'm looking into getting a puppy, and as a big Harry Potter fan, I would love nothing more than a big, furry black dog named Snuffles. I can't find a breed of dog that looks exactly like the one Sirius transforms into. Does anybody know what type of "bear-like, black dog" Sirius becomes? The closest thing I can come up with is a Newfoundland.