http://www.matrixenterprises.com/molds.htm.

The types of casters involved so far have included hobbyists and "cottage" casters that are involved in model making (Casting_Fool and SCModelWorks). Given the lack of success with the latter group, I'd try a more industrial group next.

I can start going though the list of mold maker's at Smooth-on if your lead fizzles.
http://www.smooth-on.com/mmfhire.htm

I can also contact Smooth-on and Alumilite directly to get a recommendation for a caster.