These will be up on the website shortly as well. Delrin PGP feed plugs and end caps:
I can make the grip on these custom to whatever you like, but this is the most comfortable I have come up with yet. I guess they would fit a P68SC or any other brass feed tube.
Feed plug - $8
End Cap - $4
+ whatever actual shipping is. Shouldn't be more than a dollar or two unless you're in Canada. Thanks for looking. All of my other stuff can be found on my website (link is in my sig).