That's really nice, but definitely homemade.
You can catch a brief glimpse of Mego's "Vulcan Shuttle" prototype in this commercial... like their vacuformed TMP bridge, it's more of an "impression" than a replica.
Pretty hilarious that whoever made that mockup thought a shuttlecraft would need its own tactical station
EDIT: Then again, maybe they had reason to. This picture's from the Mego Museum website, part of a handout for the 1979 Toyfair. Looks like someone back then worked out what the interior would have looked like, before it was boiled down to what you see in the toy commercial above. That's a pretty close match to the mockup.
The thought I had was that this was the concept model that was designed to inform that Mego model. That, or perhaps it was inspired directly by it? I can't remember anymore, but it is some of the most direct shots we have into it. The Mego model looks a little more open in the back, though?
I'm excited to see how Donny decides to render this.