Are you thinking cast iron because you want a sort of 3d oak leaf?
If you want 2d then how about getting stainless (or mild steel with a powder coat finish) cut by laser?
heres an idea of what laser cut profiles look like
http://www.hydram.co.uk/image_library/laser_cu t_parts.jpg
as long as the item can be drawn as a computer file (some companies will charge a hefty fee for this or may be able to scan a template) then it should be possible to cut exactly what you require.
for a one off item it can be pricey but then Im not sure about cast iron costs but would expect laser to be cheaper.
roughly what area do you live in, i may be able to help if east of england.
If not then try the yellow pages and look for laser profilers or sheet metal workers and ask for advice on laser work