Had the same problem. I just cut out a bit of the existing pipe as a sample at went to a local hardware store and bought enough to replace that pipe run.
Pressure after the regulator is negligeable but still worth doing a soap bubble test after you install the new pipe.
I did it a few years ago and at the time, I read a bit of a controversy about whether or not
a "double flare" was needed.
You need a special flaring tool to do that. (A double flare has the cut edge sort of folded back on itself for increased strength.)
I did have that tool, but in the end only used a single flare anyway!
Not a difficult job at all but you will need a tubing cutter and a flaring tool (and some soapy water and a brush!) - all readily available.
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.