My parents got a Wii the other day from GameStation Birkenhead and got a great skin with the controller. I think its actually official Nintendo and they will come with new controllers, but I found them on eBay for 99p (+ £1.79 P&P Hong Kong)!
Looks like it'll be easier to change the batteries than the normal silicone skins. Should hopefully prolong our controllers' lives as the kids keep dropping them. Plus, because they have built-in grips, they're less likely to fly out your hand when your using it.