If it's like the SLS line in my old 300D, it is 6mm if I recall correctly, and a 12mm nut. I think I got mine from Performance Tool and Supply (814-362-3221), and they had the flare tool, too. I am out of the country right now, but I have the kit at home if you can wait 'til January to do it. You are welcome to borrow it. I may have some 6mm line leftover, too.
I believe someone mentioned that
www.swagelok.com makes splice kits, too.