Try Autoglym Vinyl and Rubber cleaner. It is a UK product but you can order it from
www.properautocare.com ( I am not associated with them in anyway, just love Autoglym). Their glass polish is the best I have seen, my wife has me use it on all the mirrors and windows in the house as well.
I just got a fresh supply of the Glass polish, Vinyl & Rubber cleaner and the super resin polish for the bodywork, guess what I'll be doing to tomorrow