If you don't use a sealed container like the Pelican and Otter box options, then I would use old 35mm camera roll containers. They fit capsules perfectly. But I've never owned ck9x caps, so I'm not sure if they'll fit into a 35mm camera roll container
My old ck6x and MBHO caps fit perfect in them though. Just put some felt around the inside and some foam on the top, and you have a very efficient and effective storing option for nearly no money at all
Just go to the closest camera shop or WalMart or somewhere, and ask if they have any 35mm camera roll containers around. People still do get those pictures developed and put onto flash cards and stuff, so they're not completely extinct lol
I just leave my mk4s and mk41s on the active cables and with some DPA screens over the caps and that's it