Custom NSToolbarItem with Badge Counter

I'm trying to add a custom badge counter circle on a NSButton inside of a Custom NSToolbarItem.

It's supposed to look like this (with the red circle and a number inside):

I've tried doing it in the storyboard by adding a inline button but I don't have too much control over it's positioning and also having trouble setting a solid color to the badge.

Failed attempts:

Then I tried implementing this guys technique (I converted to swift3): http://bertmcdowell.com/posts/2013/nstoolbarbadgeditem.html

But the problem with this technique is that it subclasses the NSToolbarItem directly so I can't draw it outside the bounds of the NSButton. Here's the result:

I feel like I need to draw a custom view behind the NSButton so that it has space to draw the badge in the upper right without getting clipped. Any other ideas?

One option is to subclass either the toolbar item or the button and add a subview which draws the badge. Here's a forked version of your project which does this: https://github.com/AriX/NSToolbarItemBadge