Try Ben Hutchinson at www.inox.ie, based in Ireland, but does rapid mail order anywhere. In my experience the best stainless fitting supplier, and keeps things no-one else does. No connection, just used a few times.
Thanks to the help here I've sourced them, it was getting a bit touch and go though;
Take two M6 nuts.
Lock the two onto the end of and M6 threaded rod
Grind the outside nut until it is countersunk shape.
Allow to cool.
Take the ground nut and fit it to the end of a 150 mm piece of screwed rod with loctite
Allow 24 hours.
Make a saw cut across the nut and into the threaded rod.
One 150 mm countersunk machine screw.