How to cover this mail slot up so cold air won't come in?

Residential Mail Slots: Enhance Your Doorway mail slot cover May be used for residential door mail delivery; Made of brass; Magazine size mail slot overall dimensions are 13'' W x 3-12'' H mail slot drop box cover this with since we moved in I've checked hardware stores and searched on the internet, but I haven't really found a good cover for these I finally

mail slot cabinet We offer these interior hoods for our customers who want to be assured of privacy Solid brass, these are used with our 13 mail slot Mail Slot Hood for