O2 sensor bungs
I cannot answer your question per se, but when I looked for bungs, I ended up going to the local nut/ bolt store here and bought an 18mm nut for I think less a dollar apiece. I don't recall the thread pitch, just take your sensor down to the fastener joint.
http://www.forabodiesonly.com/mopar/showthread.php?p=1969676329
That is all in the world that this auction for 5 bucks appears to be -- a nut