I need to replace fuel line but can't find one.

Which one? There's lots of parts to the fuel supply system. Steel lines can be replaced with brake line. Rubber hoses can be purchased in bulk, but you must use fuel injection hose and clamps because it's rated for the high pressures. For special steel lines with formed ends, you can order them from the dealer's parts department. Ford is famous for parts being no longer available so you have to find them in salvage yards. GM does a better job of making replacement parts available.