Try eBay, Bias or Whitworths mail order. They will be plastic though. The secondhand marine parts people may have bronze items but there is probably a demand for them as decorative bits.
Thanks guys I'm certainly not replacing I am after an extra to put on a hatch above engine room aft in our 42 ft ketch to create some flow through ventilation !
Greetings-I am building a small Tugboat and searched extensively for some Dorades to compliment the project. DeckHardware in Sydney sells the Mainship type,Mcintyre Marine,but have a look at the Vetus catalogue which looks a similar pattern as yours.These are in S/S.I think there were some used bronze ones a while ago at Classic Boat Supplies?. A word of warning though,hold onto your chair when you receve the price!Cheers C.R.