My suggestion would be to make the blade from something moderately tough rather than mild steel, so that the thickness (thus weight) can be reduced while keeping decent strength. A medium-carbon plain steel like EN8 ought to do. Give it a slight curve along the axis of the blade using either a large-radius bottom swage or the other way up over either the horn or edge of the anvil. Weld on two 'ears' at 90 degrees to the top surface of the blade and parallel to the main axis, these ears being drilled for the pivot (for which a suitable length M6 machine-screw plus nylock nut and washers will probably do). Ideally the handle socket/tube would be a hollow truncated cone transitioning at its narrower end to a square section where it pivots between the ears on the blade, but this would be tricky to fabricate by hand. It could probably be done by wrapping a suitably-shaped piece of sheet and (fire, TIG, MIG or gas) welded at the seam, like a socketed chisel. This would give you a 'friction folder' shovel where you could add a suitable shaft when needed. Replacing the nylock with a wing-nut would give you a 'friction-locking' folder.
Or if you just wanted something to shovel stuff (e.g. coal) with, weld two sides, a back and a piece of thin-wall tubing to a piece of sheet-metal. Thin black mild would probably do.