This was so darn quick and simple, I should be ashamed of myself for even posting about it.
But I'm not, and I am.
I found those cute little buttons at Hobby Lobby for half off and had a package of the earring posts.
I took two of the small ones and clipped the ring off the back using jewelry snips.
Then use E-6000 and glue the posts and necklace bail to the backs.
That's absolutely all there is to it. So simple and took maybe five minutes!