Here is a list I found on a quick Google searchhttp://www.kovels.com/classifieds/rcsp_hardware/index.html
Let us know how you fare. I have worked with Londonderry and Monroe Coldren as well as Ball and Ball. You might ask Nancy Anderson (a wondrful person) at Londonderry if she knows of someone doing this type of work. A restorer in your area might know of a source. I have made parts from solid brass when I couldn't find what I wanted. It isn't that hard to make them look "right". You really only need a drill, hacksaw and some files. If you want the sand cast look lay a piece of 80 grit sandpaper on the back and hammer on it though that part doesn't show when it is installed.