You can buy the 6 foot lengths of 3/8" tranny lines at any auto supply store. The ones I bought had female NPT fittings on both ends and after bending them carefully from the transmission forward with an inexpensive tubing bender, the final length OF BOTH was correct to with 1/4 inch! (I could never do that again in a thousand years!).

Be sure and use teflon tape on the ends to keep any leaks out (pending any comments from the real pros on the board).