My DS(11) will keep a fanny pack (he usually wears this as a "messanger bag" not around his fanny) were he keeps his traders handy in the very front pocket (his fanny pack has multiple pockets). He only keeps his trading pins there. When he trades for a "keeper", it gets handed to me and I keep it in my fanny pack/backpack until we get back to the room. Back in the room, it goes into a plastic school box that we keep the pins in for traveling (that way they don't get damaged in my backpack on the flight!).
We love pin trading!
Lynn