What ever it is that you decide to make/use for your carry firearm, I was wondering if something like Insul-Bright heat resistant batting would be sturdy enough, would hold up well enough, to be used on the inside of your carry item? Also, Thermaflek type fabrics, the shiny silver fabrics on the one side of the hot pads, might make some good lining. Aren't these types of fabrics and batting "sturdier" than the cotton fabrics sold for quilting? Besides silver/gray, these fabric types come in various colors.
http://www.extremeheatprotection.com...ain-satin.html