Hi Max,
I had the same task few months ago. As I know there is no style exposed to public, but you can make it by yourself. This is a listbox with separators and horizontal items placement. You can find some solutions on the internet. After you can tune your solution using WPF inspector or Snoop which lets you to look inside wpf based application UI. You can find font information, triggers and other useful information.
It would be nice to have exposed to public that listbox style for future compatibility.