I'd suggest AGAINST this.
Practice in your mind over and over what you want and NEED to say when pulled over AFTER studying the laws of where you live.
Why? Where are you going to keep this card? Do they run your plates and know you have a gun before they get to the door? If you're explaining that you have a gun and are reaching for some "card" to help you out... I'd bet you are going to receive an education on how to put your face on the pavement, quick, fast and in a hurry. Or, learn how to not piss your pants when they put a gun in your face.
Just be calm, keep your hands visible and don't make fast movements. If you aren't capable of remaining calm in tense situations, you may want to rethink carrying a gun. Because if push comes to shove and you need to use your weapon, you'll need a hell of a lot more ability to remain somewhat calm than what is required during a traffic stop.
If you want this info to carry along with a video camera so you can be a Youtube star, blazing the trail to protect "our" rights... best of luck. I won't be watching your channel.
*Disclaimer* This may sound harsh. Sorry about that, but if you can't read, digest and incorporate the laws of your state without needing flashcards... your priorities aren't aligned with mine. Carrying a gun around isn't to educate anyone in the law, it's to save your bacon when all hell has broken loose.