I fixed my loose bumper strip May 2013 using a different method and it is doing just fine. I simply screwed the plastic strip to the bumper with sheet metal screws so it cannot flop or come loose from the bumper. No parts to buy or make.

Loose rubber strip on rear bumper 85 300D

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked