I found a 5/8" hole punch and leather wads seem like they'd be a whole lot less bulky to carry around than anything else.
Now, you're on to something. A 5/8" (0.625") arch punch makes perfect wads for a 20 gauge. It's a good way to use up scraps of leather, too. I've used them, after reading about leather wads in
Muzzle Blasts many years ago. This was in the February, 1955 issue, in an article entitled "M.L Shooting in the Seventies," meaning the 1870's, so you could argue that the practice of shooting leather wads is traditional.
The NMLRA has digitized all of their back issues of
Muzzle Blasts, and there is a wealth of information in them. If you're an NMLRA member, you can log on to their website to access the back issues.
I don't recall which issue, but
Muzzleloader magazine had an article by Mike Nesbitt a few years ago, in which he described using a 5/8" punch to cut wads out of wool blanket scraps. You don't want to use synthetic material. I don't recall what he used for lube, but he melted it in a pot and dropped in his blanket wads. They apparently soaked up the melted lube like sponges. He spread them out to let them cool, and used them in his 20 gauge smoothbore. I would like to try that, but I don't have any wool blanket scraps and don't want to punch holes in a good blanket.
You are right, there are almost endless possibilities in loading a smoothbore.
Notchy Bob