Do you have any audio shops near you VC?
They always stock audio covering and would sell you some with no problems. My local audio shop brought out 4 samples to the car, so I could compare them. Look in the how to section for my arch install to see the pics of the boot to see how it matches up.
You are right in the fact that Audio carpet is stretchable in both weave and weft directions and so moulds better to uneven surfaces. Carpet glue spray works wonders with it too.