Are they metal parts? There are small handheld platers that run off of a 9v battery and the companies that sell them usually offer gold, silver, nickel and chrome. The units are fairly cheap (maybe $75-$100) and then they sell you the solutions to do the plating.
I saw several vendors at SEMA last year several were dpiong things like gold plating quarters while you watched, to show the stuff. It looks cool.
I think one company was caled "Gold Effects" and I think another was "Dalmar."
Google hand held gold plating or chrome plating.
The stuff I saw wasn't for large parts (you could do them but it would cost a lot, undoubtedly.) One of them had a custom car rim in gold, but they had a larger system for sale too.
Good Luck.
P.S. If the greeblies are plastic... I have no idea how you'd do it at home, though there are paints that are pretty close.
D'oh. Just saw OdiWan72's post - that looks great and cheaper then what I saw.
