Check your local Yellow Pages for a supplier of seals/gaskets and 'O' rings. There are several types of rubber-like compounds which are gasoline/alcohol/solvent resistant. Viton, comes to mind as well as others. There are teflon seals and 'O' rings which might fit your purpose. Good luck, let us know what you find.
This is a Denver company but most major cities will have a similiar supplier> http://www.rocketseals.com/