I don't know about how things are now , but I used to get Easter stuff for my kids when they were small at supermarkets catering to Westerners such as Kinokuniya in Aoyama, National Azabu, Seijo Ishii, etc., and Sony Plaza (in Ginza and other locations).
I think they are talking about chocolate easter eggs Carlson, so PLastic ones wouldn't be that good a suggestion
I would be suprised if Japan and especially Tokyo Doesn't seel chocolate easter eggs. After all they did go along pretty heavy with the valentine chocolate gifts thingy.