Try The Paddock...

As far as I understand their online catalog they provide correct rubber floor mats in other colors than blue, red and black, too, for some additional fee....

Hope this link works:

http://www.paddockparts.com/Paddock/assets/html/FirebirdAccessories.pdf

It´s on page 38, showing a black rubber floor mat they note: special color available -- color $12.95 more.
But I´m not sure WHAT floor mats were meant -- they list them for a period from 1967-92...