Precision Scale makes a couple through-etched metal roofwalks for 40' and 50' cars.....p/n's 452 and 487, respectively.
There may be other folks who do so, also, but I just happened to have a supply of the PS ones at my workbench for several projects I've been working on. Available direct or through Walthers.
K&S Metal Products used to make this sort of material for scratch building, but I believe they gave that up several years ago.
FWIW, always...
KD