You can make your own paper tubes using sticky notes. Find a 1/2 inch wood dowel to wrap the sticky note around, of course sealing it with the glued edge. Then you tuck the bottom of it up into itself. You could then put your shot in there, and a fiber .50 caliber bore button would act as the over the shot card.

I did this with my .62 caliber smoothbore. Of course I was not spinning that paper wad around.... good luck.

If you can find someone that loads a 28 gauge, ask them for a wad. That might fit down the barrel I am not sure..