I have a few pair of aluminum soft jaws left. Bought a bulk pack of them from Monster Jaws or somebody like that a number of years ago. Turns out they don't actually bolt up to any of my vises without machining. If I have to do that I might as well just make them myself. There isn't anything special about them. Anyway, on a couple of my machines I was thinking I'd like something a little stronger, but still machine to final alignment with a step.
So what would your choice be for steel soft jaws. Obviously 1144 is since I'd have to waste a lot of material to get flat bar out it. 12L14 maybe? I know Monster Jaws sells some, but like I said, their aluminum ones didn't fit any of my vises... If I have to make them myself I might as well make them myself. LOL. Also if I machine them the way I like I can make them all double sided for different applications.