Not a good leak to have. Is that upstream or down stream of the fuel pump. On the fuel injected gas cars, the lines carry pressurized fuel.
The line will be 9 or 11 mm (about 5/16" or 3/8"). Replacement metal lines can be purchased as a bulk coil and then bent and flaired to match the original. If you have access to a pick-a-part junk yard, you might get lucky and snagg a used one there.