I have purchased Timtex at a local quilt store. It is stiff and works well cut to fit as a bottom stabilizer in a purse or bag. I cover it with a "pillowcase" of the same fabric as the bag inside.
Haven't heard of using it for cards, but imagine it will work.
I will warn you - if you buy some, shop around. It is pricy at the LQS here, but perhaps can be found for less on line.
Try Timtex, not Temtex :+) if you do a web search.
BTW, I now buy plastic canvas for crafts suggesting Timtex and cut it to fit the bags - much less expensive and works just fine in purses.