I have bought a dracco standard for my Anglo Danish army from the Donnington New Era range which is very good. I think the Roman figures are from their original range which I'm not sure about.In hindsight I would probably make my own from Milliput too, seems like a good idea. I would imagine they aren't too difficult to sculpt.
Legio Heroica make late Roman and Goth miniatures with dracco standards too although I don't know if they are cast on to the figure of not. LH are really nice figures if you haven't bought any before.