Like many people, the Mini Cooper armrest does not stay shut. This is a quick fix I performed that works great. I used 6 mini rare earth magnets that can be found at a big lot hardware store or hobby store. You will also need some super glue and probably some plastic epoxy.
The first step is to take off the center console cover. This is done by sliding it towards the back and press it towards a side and twist. It should pop right out.
Then glue a set of the magnets to the underside of the arm rest. I would make both of these point in the same polarity. A small drop of crazy glue will work.
Next epoxy them on with 2 part 5 or 1 minute epoxy. Let this sit for at least an hour to cure fully.
Then put two sets of two magnets in the tray as shown. Ensure they are pointed in the right direction (note that the top is crossed with the bottom here) and put a drop of crazy glue on bottom magnet aligned with the top location. Let this sit.
Pop the console back in by putting on side in and then twisting the other in. This holds the armrest securely and should never break. I personally don't think it looks bad either.