How can I attach angled beams to a post?
There are lots of ways to attach beams to posts, and you don't necessarily need purpose-built brackets. Miter your beams so that they come together at an appropriate bisection of the post top, and use whatever means is convenient to keep them positioned... dowels, angled screws, etc.

In the case shown in the second image, I'd be inclined to use a skewed hanger and hang the angled beam on the other two. If your beams actually have the offset shown, things are complicated a bit, but maybe a short third member bolted to the right-hand beam would flush things up in simple fashion.