In case you ever need a small one off casting in bronze (or brass/aluminium) the chap here seemed very helpful. They would just need a sample or model made of wood and seemed to be reasonably priced. Fortunately I found what I was looking for in stock at Classic Marine but will keep this for future use. He says they often get to do bits for boats.
http://www.adcastings.co.uk/ (Blackburn).