While not 100% what you’re looking for, since it’s a story about relatively early Christianity in which a saint is converting pagans rather than rectifying church practices, my favorite traveling bishop story is the tale of Saint Martin of Tours and the pine tree, as related by Sulpicius Severus.
The short version is this:
Martin had traveled to a town and destroyed its pagan temple, but what was left was to destroy a pine tree that had been dedicated to the pagan god. The people of the town, who had stood by as the temple was destroyed got really incensed at the idea of the tree getting cut down. But Martin insisted, as the tree had been dedicated to what was, in his eyes, a demon.
So the people agreed, under one condition: they themselves would cut down the tree as long as Martin would stand under it. At this point, they would rather kill the guy who wanted to kill their tree than keep the tree itself. The tree was already leaning a little bit, so there was no doubt where it would fall. They tied Martin up and put him in this spot.
They began cutting down the tree, and Martin did not seem concerned at all. With a creak and a groan, the tree breaks and begins crashing towards the earth. Before it can reach Martin, however, the man of God makes the sign of the cross in the air, and the tree spins around like a top, falls backwards and nearly (but not quite) crushes the men who had cut it down.
Obviously everyone was super impressed by this and converted to Christianity immediately, hoping to gain their own tree-repelling superpowers.