Dytac does make the MK1. I have one attached to my G&P AEG body. Came with it's own barrel nut and installed on my G&P flawlessly.
Now it is a little longer at 10" instead of the 9.5" so i'm not sure if that's an issue for you? I also briefly had the MK5 Keymod 9.5" and that also installed flawlessly.
http://store.specwarfare.com/en/dyta...rofile-black-2
http://store.specwarfare.com/en/bd-m...r-416-rails-bk
Specwarfare is just one place that carries it but there are others. Only seems to be the HK stores that carry the MK1 though. I haven't seen them over here at all.
Anyway, just food for thought.