I went on an Easter egg hunt last year. Here's what I came up with. None of these eggs said, "Contains traces of dairy".
Cadbury Old Gold single eggs (Your choice whether you want to buy from them). About 50% cocoa. Available from large supermarkets such as Woolworths.
Alpha has various boxed ones - quite delicious too. There are single eggs and some accompanied by plum or apricot chocolates.
About 50% cocoa. Found them in IGA supermarkets, Myer and David Jones, Big W etc.
Alpha also makes mini-eggs but they're not as good - taste fatty. However, they're more widely available.
Constant Craving (from Australian online store vegano). Super indulgent - a few varieties.
Lindt 70% dark eggs in a box with mini-chocs (not sure about the traces of dairy with this brand). Saw this egg in Woolworths.
David Jones also has quite a few brands of dark eggs. Didn't try them all. The best one was a brand called 'Praline Chocolates' There was Irish Cream or Truffle which were vegan. They came in a gold tin consisting of a medium sized egg (and a very good quality and delicious one) and 6 truffles in foil. Not too expensive either.
PS As mentioned, Sweet William have soy bunnies in many supermarkets. I personally didn't like them much.