Hello and welcome to the forum. All is not lost with the watch post some pictures of the movement with the back off Screws and battery clamps can be bought. so like Lazarus we MAY be able to raise the dead .
Steel is what you want. Preferably stainless. Get a magnet- good quality 304, 306, 316 stainless alloy will be non magnetic. Try ofrei and kas-ker. otherwise vintage NOS is always good but like we talked about-can get spendy.
Otherwise some can be cheap tin or aluminium. Even plastic.