I've been trying to find the perfect cup holder for my w126s since I bought the first one a couple of years ago. I didn't want anything that would attach permanetly so that limited my choice. I hated everything I tried. Then I was doing a search on the forum and someone metioned Fischer as really high quality, German made product, I followed their link, liked what I saw and ordered two on the spot. They shipped quickly and the cup holders are top, top quality.
I live in a small town, work from home and most trips are pretty short, but when we travel, or drive the 100 miles to Chicago to see my kids and grand kids I really want a cup holder. I just don't want it in the way when I don't need it, which is most of the time.
I studied the Fischers for a week and finally came up with a solution that works really well, for me at least.
I used 3M Super Strength Moulding tape to stick them together
in what would be the vertical mounting position.
When folded out they form a nice stable base.
But when folded up they tuck nicely at the back of the
console tray, leaving most of it open for whatever . . .
When needed I lift up the arm rest . . .
Slide it forward . . .
For one cup you can open the front one . . .
Or both will make it a little more stable. As you can see
the arm rest will fold down even when both are open,
though to use the back one you'd have to raise it.
Even though the cup holders are just resting in the console tray
and do move around a slight amount, I've never had a spill,
even with both fully loaded.
Then when you don't need 'em . . .
They're tucked out of the way but instantly available.