Artist: Shunshell
I don't think Nightmare Moon is terribly enamored by her quirky plush counterpart. Sorry, Moonie. You're going to have to commission someone if you want a decent accurate one. Evening, denizens of the night.
Someone named Wintergleam apparently constructed the pony solar system by analyzing a bunch of screenshots from various pony mdeai over the years. It's apparently 300 pages long if you want to go read all about it!
Thanks to Squeaky_Belle for the heads up.