Get it from chickens, much easier. On chapter 3-1, on that small island in the middle of the map, theres 6 chickens, just stay there and wait to see what kind of egg they lay. Its not confirmed but for my experience, amateur level its easier to get golden eggs. I got 3 of them in one run on 3-1. Good luck!!
Simply change Sheva to Attack mode and go watch some tv, Sheva will help you pick any egg the chicken lays. :lol: