speaker surrounds

Hi does anyone know where you can get 'real' speaker surrounds like good quality synthetic rubber or impregnated fiber roll instead of this rotting foam crap that is so readily available. I have speakers with both the fore mentioned surrounds which are more than 25 years old and are like new in compliance. Why the foam?

So you replace the foam with more foam and in 20 years you replace it again. What's the problem? Or do you want to change Fs by altering the surround design?