We find the Bullet Head nails from bunnings work well
You could get 3, 4 or 5mm diameter mild steel round bar from a steel supplier very cheap – this is a softer iron alloy so it will rust more readily
Black rod ties, for rebar etc. Although it seems completely contrary to what should actually corrode, I’ve found the “zinc plated non-galvanised” type from Bunnings actually rust the best.