At our local Asian market we have these puffy chips that are made from shrimp--HIGHLY addictive! Are those what you mean by prawn crackers? These are made from tapioca flour and shrimp. They come in a variety of flavors. They are called Marco Polo Shrimp Snacks.

Connie Mistler Davidson-Editor-ADD/Sandwiches/Reading
Attention Deficit Disorder
Sandwiches
Reading
Avatar: Hope~Even when conditions are harsh, hope can bloom.

My EBook link.
Building School Success with ADD EBook Link