What are you looking for in a sleeve? I've just standard neoprene Case Logic for my 15" MacBook Pro. Serves me well when I haul my machine around in my backback. I also have a Booq case that I purchased when I purchased my Booq backpack - I don't really care for it although it's a 'snug' fit.
If I were you, I'd just do some searching on Amazon... you'll surely be able to come up with something.