Jules, link to Krank's site page for wad punches: https://www.henrykrank.com/muzzle-loading/muzzle-loading-tools/wad-punches/
I have used horse saddle padding which you can find from a saddler. They will often have offcuts that they just throw away. This is another source I intend to try: https://chimneysheep.co.uk/collections/new-in/products/wool-pipe-lagging Cut and sandwiched between card wads. Lagopus.....