I talked to Apple support on the phone two days ago and was able to order two extra female to female lightning adapters for the Apple Pencil. They cost $4.95/each plus $6.95 shipping...shipping time was overnight. They also sell the end cap. Unfortunately, Apple has not decided to sell the Apple Pencil parts through the Apple Store, I have no idea why.
Not sure if you need Apple Care to speak to someone, I have AppleCare+. Be patient when you call Apple Support because it took me about 72 minutes to finally find someone that could confirm they could sell me the charging adapter. I waited 12 minutes to speak to a tier-one support rep. He had no idea what the adapter was. He decided to transfer me over to the Apple Store sales people even though I told him the adapter is not for sale there, had to wait about 10 minutes for those people. They also did not know what the adapter was. Then he transferred me back to a tier-one support rep who again had no idea what the adapter was, had to wait about 15 minutes for him. Then I got frustrated and demanded to speak to a senior support rep, and waited about 15 minutes for that person. They actually knew what adapter was, but it took them about 10-15 minutes to confirm they were able to sell one to me. I decided to order two so I did not have to go through this insanity again.