Might be worth trying your FIAT dealer. When the Stilo was still on sale new, proper silver plastic overlays (not stickers) were available as a FIAT accessory. Actually saw them illustrated in the Stilo accessory brochure at the time.
where abouts do you live? as a lad I know owns a bodyshop and deals with modified cars and probably will be able to spray the vents and windows switches
sorry to bring up an old thread but does any one have a five door with silver vents in if so could you check eper with your chassis number and post part numbers please just for the driver and passenger side i have spoken to a dealer not very helpfull because mine are black as standard