Parsley would be a great substitute. My german Nana used to make us great potato pancakes which were similiar to these - grated potato, squeezed dry, a bit of flour, eggs and TONS OF PARSLEY - I mean, she put HEAPS of parsley in there, bless her. To this day, whenever I think of her (she's passed now, a long time ago) it's usually when I'm eating parsley. She used to have FORESTS of the stuff growing in her garden. Plus, the german word for potato cake is kartoffelpuffer, which is the best word ever. Right, I'm definately heading to the kitchen now...