Manually enter an author name on a blog post

Hi, I have a blogger client that occasionally has guest authors and doesn't want to create a user account for them. He had a plugin called "Manual Author Input", but it's old and it started crashing when I changed hosts. The plugin seems to have disappeared off the market and I'm not finding anything similar. In a nutshell, it just lets you easily override the author name shown on a blog post. The attached screenshots show what I'm trying to accomplish (These screenshots are from before it broke). Anybody know of anything similar or a good way of doing this?