The company I work for has a product called Geomembrain or something like that. It can be used as a pond liner or for bigger jobs like soil reclamation and such. We don't sell much of it so I don't know much about it...it's expensive though. That doesn't really help but I thought I'd let you know.
If there is anything the nonconformist hates worse than a conformist, it's another nonconformist who doesn't conform to the prevailing standard of nonconformity.