Way back on the technology evolution time line, there was a period when a properly dress geek felt naked without a pager and there were these
universal belt clips that you could get anywhere.
If you don't like the idea of pocket lent, about all I have in my pockets, contaminating the lens cap and then transferring to the lens, this might be a way to go. Stick the disk to the front of the lens cap and clip the holder to your belt, bag, bill of your baseball cap, or maybe a lanyard around your neck.
There are also the
Optech Flilter Caps.
Thank you
Russell