Author Dropdown list and more

I’m trying to set up a sort of complex filter search for our blog posts.

I have one set up on https://wmbactiveblog.us/blog/. Click the Show Filters button to see the criteria I have set up with Search & Filter Pro. I’d like to do something like this, but with Ajax Search Pro. I like the way your plugin works much better.

Where I am getting stuck is how to make a drop down list of Authors as part of the filter.

We have a search field, Category checkbox, Tag dropdown, and Author dropdown.

Can you help me get there?

Thanks