If a bolt breaks I'm not concerned about replacing with a Jis head bolt. I just need something to get me home. And once I'm home, why would I replace it with used, rusty, rounded off bolt from a junkyard? Especially since it seems to be a failure point? I would replace it with new oem, or better. since it's cost prohibitive to carry a bunch of new general toyota hardware, I carry an assortment of new decent quality various sized metric hardware from belmetric. I think paying money for used hardware is silly.
For things that are *common* failures, I carry new Toyota, like control arm bolts, shock bolts, lug nuts and studs.