Well neither Jeffrey Schwaia's suggestion or Robert Steven Fish's 
suggestion was a winner. The 13 pin connector that the Europeans also 
use is just as foreign to the US shores as the 7 pin connectors.

On the other paw, I did locate (using Google instead of Ebay.de and 
searching on "Anh�nger adapter") one vendor that sells adapters (from 7 
to 13 pin) but instead of a solid adapter, the two ends are connected 
via a cable. This sounds like a possibility (allowing me to cut up and 
rewire the adapter, rather than my Vanagon.)

The cost isn't all that much (though the shipping issue might be.) I 
just have to figure out if it really is worth the trouble.