I’ve just sold a $200+ gift card on eBay. I would like to insure it, but I was wondering if USPS would accept insurance on an envelope containing a gift card if it was mailed using First Class Mail? If not, should I put it in a bigger(6×9 in.) clasp envelope or mail it using a different service through USPS? I don’t want to spend more than $3-5 in shipping costs.