You'll have to be a little more descriptive than your post. Are you talking about the roof bar that goes from one side to the other, or are you talking about the little rubber pieces that go at either end of the t-bar itself? If you are actually talking about the roof bar, the correct way would be to remove it, resurface it, then refinish it, however, that would involve cutting it off, then urethaning it back on. If you were to do it that way, you would probably spend near $400-$500 at a bodyshop that knows what it's doing, at least in my area (rates are around $80/hr.) You could paint it on the car, however, overspray is a huge concern and you may not be able to cleanly refinish all surfaces, leaving edges looking pretty crappy. You'll save a lot of money doing it this way, but as is with most things, you get what you pay for.
Good luck and I hope it works out for you
