Substitute parsnip root for the parsley root if desired. Substitute 1 small celery root, sliced, for the celery stalks if desired.
Substitute ground turkey or pork for the ground beef if desired. You can make the meatballs small, medium, or big, but no bigger than apricots.
I found lovage online. If you can't find lovage, use lemon salt (not the same thing as lemon pepper). I've also used just the juice from 2 lemons when I couldn't find either, and it seemed to work well.