Looks like some young man from Poland found 'the business idea of the year', he produces the rubber for the keys for E38 and E39, which wear out terribly and the dealer only sells new keys.
Some people from the German board already have bought it and they are happy with it.
EURO 11.50 plus 2.50 for shipping within/to Germany from Poland beats the dealer price of >130 EURO for a complete new key.
Not mentioned that he ships outside of Germany, but give it a try.
http://search.ebay.de/_W0QQsassZkim9.888
I assume it even might fit for E32 and E34 RF remotes, although the trunk button logo is different.