If you know of a local market with a good fishmongers ask them to get you some. They may not stock whitebait usually because i guess there's not many people who want it but that doesn't mean they can't get it if you asked for it specifically. I used to keep pirahnas many many years ago in my first stint in the hobby and i used to feed them whitebait. I must say though i probably got through more than the fish, you can't beat whitebait shallow fried and splashed with lemon juice, hmmmmm.