Plastikote spray would work, I think it peels off if you fancy a change too.Just a thought, you used to be able to buy paint for colouring plastic trim like this. I think it was called bumpercoat or something similar.
All you had to do was clean the plastic properly to remove any contaminants such as silicone and then spray it on.
The colour would change but the grain would remain. I am sure dark grey/black would look original.
edit: Just looked on ebay and there are several different makes of paint specially for bumpers...