looking for info on roof rack crossbar parts?

does anyone have a part number or know of a eseller specifically to order replacement plastic crossbar connector brackets vs buying a whole new set of crossbars for the roof rack? I seem to go thru these fairly regularly when the garage door doesn't quite open all the way and my empty bike rack catches. (black plastic pieces that connect the aluminum crossbar to the side rails). Seems the parts catalog gets down to the nut and bolts on everything else but have not had luck locating these. or . . does anyone know who might be rhe oem manufacturer? thanks