Daniel sent me a message, to give me the email address of a guy here, who's gotten some from Germany.
I'm getting kind of excited about this.
I remember my dad trying to figure out how he could keep the Natrix out of his fish ponds without hurting them. He had some big goldfish in one pond and Karp in the other, and he finally ended up covering the ponds with fine chicken wire during spring.
I also remember him talking to somebody about this who asked him why he didn't just kill the snakes. He just shook his head and said something like "why on earth would I want to do that?"
Our Natrix were just dark grayish brownish, with very subtle patterning, and pale belly, but when the sun was on them they had a lovely, slightly coppery sheen to them.