A little off the point but if you're prepared to give it a go yourself have a look at Humvee Graphics. I wrapped my top box and panniers in black with their product to disguise the oxidation which seems to be unavoidable on BMW aluminium. I found it quick and straightforward to do (good demo videos available) and long lasting - been on for a couple of years and still as good as new. If I recall correctly the total cost was around £120. Recommended by a number of posters on here and I endorse that recommendation