if you cannot find a plastic card holder for them see if your local get well card shop sells gift card sleeves, they are almost hard cardboard sleeves made to keep gift cards safe while they are inserted into cards get about 15 or 20 in a pack for like 2 or 3 bucks, slide them in and tape the end shut maybe, to make it better you could actually send it inside a thank you card, most times cards are treated with more care when mailed then regular mail :-)