If your keyboard is also available as a German version, one way would be to look for someone with such a board, who replaced all his keycaps. Then you could pick from his set the keys you need for your keyboard.
If you want to buy a new one: There is no such thing as an ANSI keycap set with German legends, if that's what you're asking.
You would always need:
One standard set (which is practically always ANSI with US legends)
+ one accompanying extension key set with the German keycaps (these kits are usually called "international kit", "NorDE" or "NorDeUK kit")
The problem is: These combinations are often available in group buys / on massdrop, for which you need a lot of patience, but usually not in stores to buy off-the-shelf.
You can try to buy them used, but it is quite rare to find them in combination with an "international kit".
