You can buy spray cans of SEM Bumper Coater at most big autoparts stores or paint suppliers. It's fantastic stuff. Sticks like crazy to all vinyl and rubber trim items, and lasts about 3 years when the car is exposed to the weather. Longer if car is garaged or at least protected from sun.
It's a professional grade product, dries almost instantly and does require you to mask off the bodywork. We used it on almost every car at the dealership I worked at- even 2-3 yr old cars can show some fading on rubber parts.
You'll be very happy with the results.
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Rob Bareiss, New London, CT ::: 86 244DL, 87 244DL, 88 744GLE, 625K Total