Anything used for storing credit cards, instax photos, trading cards, or business cards will fit Yoto cards (excellent design, Yoto folks!). I use a business card holder, like the one pictured above, and snipped a little corner out of each slot for easier card access. It cost only a few bucks on Mercari. You can also buy business card insert sheets for any old A6 binders/planners you have laying around. Search “cash stuffing binder” and you will find tons of cute ones to which you can add card inserts.