Making custom passive membrames

Hi everyone! For a project wich has to go loud i need a custom passive membrane. I contacted some companies but the costs are to high. Is there someone who knows wich rubber is used in those surrounds and is it possible to make a custom myself with a malt. In theory it should be possible ofcourse but i don't know the rubber "ingredients" and thus can't find it on google. There are flexible silicons but i think it's not strong enough to make a surround...

Thanks