On my '07 400h, I noticed that the rubber cover has become sticky with a few cracks. The dealer confirmed that the entire switch has to be replaced. The part is $78. As a cyclist, I have a few spare patched inner tubes around. I cut a tub to match the size of the rubber cover. I glued the tub over the rubber cover with contact cement. It is probably not a long term fix but a lot cheaper than replacing the entire switch. Ridiculous that the rubber cover is not sold separately.