I believe there is a pourable Epoxy made by Devcon
We are trying to avoid the traditional multiple layers of glass here .
I've had great success with resin and sand , ratio of 1 / 5 , very similar to concrete . A bigger mould I just made came out great , super strong and rigid , but heavy . Next one I will fill same space with foam , it will be poured in 2-3 stages to avoid build up .