According to the dealer, the Chrome Cowl Vent Cover is no longer available (even in Germany).
Checking many sources (such as Millers), I came up dry. But then I lucked out! Bud's Benz had one left so drove out to Douglasville and picked it up today (mine has a small piece broken off so rechroming wasn't an option). It's amazing how precious it seems knowing it's the last one. Hopefully, DB will re-manufacture it soon.
Best Regards,
J. P. Mose
1968 250SL
1987 560SL