So as it turns out the white promo boxes fit the settlement event cards perfectly. But I wanted to dress them up to fit with everything else in my core box. So I made some printable stickers designed using existing KDM art to wrap around the lid of the box.
My printer has a 2cm margin so these sheets account for that and are slightly smaller than your standard 8.5 x 11 page so that your average printer will usually not try to resize it. Print them out in portrait mode on a standard 8.5 x 11 page.
I printed them out on plain white "sticker" paper. Cut it out and then carefully stick the top edge on and the do the rest and fold the wings all the way around to wrap the box leaving only the corners slightly exposed.
I like to use the "Settlement" sticker on one box to store my current settlements innovations and gear cards between play sessions. And I use the "Events" sticker on another box to store all the settlement event cards.
Maybe it's something about the photo or maybe it's whatever, but dang...that's a really nice-looking print.
Plain old Epson printer set to print on white plain paper at photo quality. The paper itself is special paper that is a giant sticker so the backside is adhesive with a wax backing that peels off. Maybe the backing helps trap some of the color during printing.