Wads, lubricants and I believe, brass cases can be purchased at www.trackofthewolf.com . They have been a great supplier for me for BP stuff as well as brass for normal BP ctg. guns, 3-1/4" and .50 cal too.
: Recently, I saw an add for 12 bore brass in a gun mag. It was $23.00US for 2. I believe it was either a Rifle or Handloader magazine.
: NEI makes moulds for about all of the original bullets for the bore rifles, at least to 10 bore & probably will make any size wanted, but they are very expensive.
: Jeff Tanner in England makes RB moulds any size for $24.00US or there-a-bouts.