I've done some work for the special effect - film and theater industry.
There is a small magazine/book title you can pick up at Barnes & Noble or other large bookstore called CineFX. It's a quartely pubnlication I think, found on the magazine racks.
In there, look through the advertisers.
There is a company located around Redmond, WA that makes a moulding material. I forget what it's called though. It holds exceptional details, dries VERY hard and durable.
If you need a male mould, just pour some of this into the female mould and let cure.
I'll do a bit of searching to see if I can come up withthe name of this stuff. I haven't used it since the early 1990's. I do recall it was not very cheap, but it was very, very good stuff...
EDIT
I found it. It's called Smooth-on.
http://www.smoothon.com/
Apparently, they are no longer located on Redmond...