I don't think there's one that is too similar to Julian, but f I had to choose one it would be the most obvious: Gabriel Jesus. A "smallish" center forward that is versatile enough to play any attacking position.
I do think Julian is more clinical as a finisher and hopefully that bridges the difference between a good serviceable squad memeber as is Jesus, and a future star, which is what I think Julian has the potential of becoming.
The thing with Álvarez is that, at first glance, he doesn't wow you with anything:
-He isn't the fastest guy around, but most times than not, will win a race vs the defender. He has a special knack for stealing the ball off goalkeepers and defenders, as I'm sure you would have seen in some of those youtube videos. It's almost as if rivals don't expect him to be quick enough to get to them but he presses the turbo midrun and nabs an out of the ordinary number of balls from opposing keepers and center backs.
-He also doesn't have the flashiest of dribbling techniques, as I'm sure some of you also might have noticed from the video. It looks kind of clumsy, sometimes it seems like the ball gets too far from him, but the kid never loses control of the ball and always seems to get where he wants to.
-The one thing that does stand out is his accuracy to hit it between the posts. I don't have it at hand but there's a stat out there that shows that the dude has an abnormal rate of shots on target. The keeper might save it, but Julian doesn't send it wide or above. And I don't know if it's still the case, but at some point last season he was the player with the most goals outside the box in the World behind Messi.