Marks... I'm getting ready to do this (spitfire MC), and I think I will use a length of brake line that I have with my 'stuff'. It's about 20 or so inches long with a ISO/DIN 'bubble' flare at each end. I plan to cut it in half to make the jumpers. Then I'll cut the ends off the old original brake lines. I'll join those with the jumpers using SAE standard 45 degree (US style), common flares. It will be easy to make the flares, and easy to get the couplings. You may have difficulty finding the 7/16 tube nut that you'll need, as Joji points out.
You can probably get a piece of brake line with the bubble flares at each end from Moss Motors, British Parts Northwest, or some other place. Maybe Ray at RD. You don't need to be fussy about the length, as long as it's enough.
This kind of tool, OEM tools 24364, makes a good 45 deg flare. ~$25.
-V