More creative juices flowing this weekend. I sat down and created multiple spinners. This one uses (3) 1/2" nuts, (3) 5/16" nuts and one 608 bearing. You can leave out either the 1/2" or 5/16" nuts and it should still spin pretty good.
I designed this one to be 7mm high which allows the 1/2" nut to stick up about 4mm but the bearing and 5/16" nuts will sit flush. You can shove/hammer the 1/2" nut in 2mm if it really bothers you.