Typically the LBS has to order a blank black spoke, then cut and thread it to size.
TxAventon, that nipple will rattle around until you remove the tube valve and let the nipple fall out of the valve hole.
I got a reply back from Aventon and they said that it is intentional. They said that lacing the 12 gauge spokes alternately would put too much pressure on the spoke heads.That is strange and I have never seen it done that way. I'd send Aventon an email and see if it is intentional.