Unfortunately, I have the same key wear issue. The key blade is molded to the actual plastic, so the only way to fix it, would be to order a new key from BMW. I bought a new key on eBay in hopes of changing out the rubber buttons. All 3 buttons are part of one piece that is bonded to the plastic part of the key by very strong adhesive. Even when I removed this piece, I found it impossible to refit this piece on my old key without tearing it. Momentum BMW in Houston can get the key made in about 3 days for $100 + tax. All they need is your car's VIN and a copy of your title and drivers license.