Replacing Carpet

We are replacing the carpet in our 91 XJ, the original carpet had heat shielding attached to it (fiberglass looking stuffcover in clear thin plastic). Our new carpet kit dosen't have this shielding with it. Is there a place to purchase this heat shield or what material can be used instead
Thanks

JC Whitney sells some silver-ized heat shield/soundproofing mat for not a lot of money. That might do it for you.