Depending on the year of your 280 you may have a different tire pressure label. If your car is a 1971 USA model it might have had a purple label. If so these are still available new from Mercedes for about $11 -$15, depending on the dealer you buy from. I know you have the label, but in case not correct for the year, you can get one with adhesive.
Part number:
113-584-00-39