I got one of these from Jaycar. Pluckable foam, shoulder carrying strap, small key lock. All for $40.
http://www.jaycar.com.au/productView.asp?ID=HB6355
There alre a few different ones in the store so have a look a look around (I used their search engine with "aluminium case" entered) and see what one takes your fancy, or to compare prices with other stores.