Fixed mine now.
When I got the car I only had the white piece sticking out the side of the seat; no switch cover or piece of rubber covering.
Got the switch cover for about NZ$12 (so about US$9) from the local BMW dealer, then went into my local marine shop and got a piece of rubber tubing that just squeezed into the switch cover. Rubber is ~8mm outside diameter and ~5mm inside diameter. Cut to length and push fit. Cost of rubber hose NZ$1.
Works very well and takes a decent amount of force to pull the switch cover off. So total cost about US$10 and less than 30 seconds to cut rubber to length and fit. If you're intelligent enough to know how to breathe then you should be able to do it yourself. Only tool needed was a Stanley knife to cut the rubber to length