Here's a tip for all who want to make this but don't have a steamer: Get one of those tiny battery powered frothers. Can't remember where I got mine, but they do a great job, they're cheap, and they're easier than a blender.
Vanilla syrup is usually in the supermarket coffee section.
........Can also use droplets of vanilla extract.
Those frothers are nice.......I have one.
But I’m guessing everyone has a blender......which does a great froth.