Go to the Micro Mark Tools web site and put in "casting resin" under the search block. I have used this stuff for scale R/C airplane parts like exhaust stacks and also a scratch built Nautilus from 20,000 Leagues Under the Sea. The Nautilus has 48 teeth which needed to be cast.
The kit comes with the rubber you will need to make your molds and the resin, if your doing small parts this stuff will go a long way. The only issue I have run into is that the molds do not last much more than 15 or 20 parts then you will need to make another mold.
Its a really cool process and the results are usually pretty good.