Gary,
Would all these foundries that you've already tried be considered top of the line, or are they more like commercial mass production foundries that basically produce home decor type castings?
To be more precise, would a top flight artist take his projects there to have his work cast, or would they go to more specialized (and expensive) foundries where the artisan's possessed higher skill levels?
If the answers to the questions above are yes, is the reason you're not taking the project to these better foundries, because the cost would be prohibitve?