Flexible brake lines have not been made for decades other than the more recent "concours only" version so not allot of choices. The goverment mandated double crimping of the flex line to ends in the 70's so allot of NOS/Service parts are of the upgraded style.
Here is a thread discussing the subject. Not sure as of this moment who, if anyone, is reproducing the single crimp style. These things change so quickly
https://www.saacforum.com/index.php?topic=3225.msg28481#msg28481Flex fuel lines have been available for decades. There was only one maker handled by many of the catalog shops May be two suppliers now. Chances are that if you order it from any where your getting the same thing
Solid lines can be a challenge since most are bent for shipping and need to be reshaped once you receive them. Haven't had to purchase any in the past year. Maybe someone else has and has an opinion on the brands and suppliers of currently available versions