As far as I know the only magnesium bodied cameras are the pro or near pro spec models (5D, D300 etc). Mag alloy costs...

Ffordes have an Olympus E1 or two... Otherwise I suspect you will have to save a bit more dough......

I find both my plastic cased Canons fine if occasionally a bit squeaky/creaky when gripped in the wrong place. Fortunately both have a metal chassis which may not be true of some budget models...