Malcolm, the case latches are usually called Over-centre hatch or latch fasteners or just hatch fasteners, and are available from most boat supply stores or even from Bunnings hardware (which is where I sourced mine for the case). There are three sizes, the smallest were used on the case. In Bunnings they are usually in the aisle where the hinges and case locks etc are located. They are in a Blue blister pack. If you want to order them online they are available from Whitworths Marine at
www.whitworths.com.au and are catalog number 42071 (the small ones - which have an adjust able length of from 85-95mm) the small ones from Bunnings are a little smaller.