Here are some links that may give you some ideas but please try to be creative and make something unique. I notice that lots of the Pound Shops have bonnets and chicks etc for sale. Otherwise you could make the bonnet out of card (cereal packets), papier mache, an old hat (you can often pick these up for 20-50p in charity shops – it doesn’t matter what it looks like as you are going to customise it. It shouldn’t end up costing you (or your parents!) a lot of money!
http://www.bigeyedowl.co.uk/craft-ideas/Easter.htm (scroll down the page)