They are here on TMC. If you can't find them, I can go back and snap a photo of them in my 60.
Wow. Google Images has none. I'll go take a photo.
Rear cup holders in Tesla Model S 60D built in November 2016 VIN 166xxx:
If you touch them by accident, they open up, and if you want them open, they are a chore to get open. They look better and probably last longer than the ones in my old MBZ.
I don't think my car has the flop down armrest cup holders. I'd have noticed every time I flopped down the back seat backs to get at the trunk.
My car is due for a washing. I have cloth seats. As another poster said, I think the 60 and the P100DL have the same rear cupholder. You'll probably get spiffier seats, though. I do have Premium Upgrade Packages, because that's the only way they bundle HEPA filter which I wanted, so my car is a weird mixture of cheap and nice.