Power seat track question

There are four black plastic rail bushings that run the along the length of the track rail on a 1999 Grand Prix power seat assembly. One of mine has desentigrated and the local dealership cannot seem to locate this part number from any current inventory. The number stamped on the bushing is #16776142 and this appears to be a valid part number. Does anyone know who the vendor might be for the Grand Prix power seat assembly? Can the seat still be operated, minus one bushing, without further damage to the seat? Any help will be appreciated....

It appears that GM no longer offers that bushing/bearing separately. Are the bushings you need under each of the 4 hieght adjuster actuators? IF so. then you have to buy the adjuster to get the bushing/bearing.