If you want firing pins, John (master22nl) said he had them. Complete bolts and bolt parts have all but disappeared for the SG43. I put together and spare bolt by buying a stripped bolt from Apex and by buying a bolt "re-build" kit from John - that way I had extras of everything, not just a spare this or that. I actually bought two bolt rebuild kits from John. Not the cheapest way to go, but it's done and I have a supply of spares the will last me a while. I don't know of John or Apex is still selling those parts.
John has some, but not all, spare parts for the SG43 in pretty good shape.