If they are factory you should be able to find them here.
http://www.gmaccessorieszone.com/index.php?id=132&tx_gmshopb2b_pi1[division_name]=Chevrolet&tx_gmshopb2b_pi1[vehicle_name]=Suburban&tx_gmshopb2b_pi1[year]=2008
http://www.gmaccessorieszone.com/index.php?id=132&tx_gmshopb2b_pi1[division_name]=Chevrolet&tx_gmshopb2b_pi1[vehicle_name]=Suburban&tx_gmshopb2b_pi1[year]=2008