What are all the promo cards available for Dominion?
According to "Hans im Glück", which is the publisher of Dominion in Germany, there are only those five promo cards available. At the moment they sell the german version of the stash (Geldversteck) and the Governor (Gouverneur) in their online store http://www.cundco.de.

They also say that as soon as they are out of stock, they wont sell any new cards. 

There is a german Dominion big box available at amazon.de which contains all promo cards. The description of the Dominion big box at amazon.com, however, says 


  Additionally it contains promo card sets which may vary 


So this box will most propably not contain all of the promo cards.