I get them made up at a local hydraulic shop. The flex line is aeroquip; the ends are from a variety of sources.

I originally just gave them stock hoses to duplicate in teflon stainless braid.

If you have a "popular" car, you have many off the shelf options, like goodrich, SSB, etc.

I had SSB duplicate a set of factory hard lines for my last build because the original were getting a bit "crusty". They did a real nice job.