I rebuilding the rear suspension on my '73 914 project car..........I find that the part called a "supplemental spring" in the factory repair manual is no longer available anywhere, apparently. Since it is a "bump stop", is there a replacement of some kind from another Porsche or ???? Koni makes some, but they don't fit the rear shock. My shocks are Bilsteins, but I haven't found any replacement parts for them in their website. Thoughts/ Advice??

Not needed with Gas shocks, I leave the washer part that is left after the rubber falls off.