Go to your FLAPS (friendly local auto parts store) and buy some brake lines. It is European metric bubble flared brake line. Any short piece of 914 hard brake line would be a good sample. Take your caliper with you and make sure it fits.
I took a short section of brake line with a fitting on it when I went. Unfortunately, the line I found locally has a different size hex on the fittings so that doesn't match the rest of the fittings on the car, but they work out just fine.
All the calipers have a stub of hard brake line entering them. The hard line then attaches to the flexible brake hose (double female ends).
Good luck to you.
And get that car done. And how was the PW derby? We need pics.