OIC
A few options:
paint them with heatproof paint in the colour of your choice.
Shine them up with fine wet'n'dry.
Go to an exhaust place & ask the guy for some suitable diameter stainless offcuts from his scrap bin & polish them up & have the exhaust guy tack-weld them on.
Go to exhaust place & buy from their selection of chrome tips
Go to car accessories place (SCA, Autobarn) and buy tips & fit.
Buy Genuine accessory tips from VW