Just pick up a used set of rear armrests from someplace,cut out your location for the speakers and buy a section of matching vinyl from a place like SMS who has all the factory colors to match.You can actually use spray on adhesive(buy the good stuff from 3M) to hold the vinyl to the armrest.Use a heat gun or blow dryer to heat and stretch the vinyl and smooth out the wrinkles.Always start from the center and work your way outwards towards the edges.