I did a rough sketch and showed it to a randomly chosen shop proprietor who pointed across the road. Initially I thought she was trying to politely fob me off but to my amazement I had directed to a shop that specialised in cast hand wheels, pulleys and chain sprockets. Unlike Melbourne suppliers these guys held stock!
Well worth a look at the engineering suppliers around the Odeon Circle Monument. Specialist shops for stainless marine fittings, bronze hardware and lots of metal merchants. Make sure you get lots of baggage allowance.