Aren’t you stacking the deck just a bit on this? I mean anyone around Jesus, who knew him well enough and followed him around enough to be convinced by his claim to be God, would have been convinced by him and would have become Christians. Aren’t those precisely the claimants that you disallow a priori? Speaking of bias, shouldn’t you take all claims into serious consideration on their own merit, rather than dismissing some merely because they favour an answer you don’t approve and want to disprove? I mean most of these people had first hand access to all of the facts and were convinced by those facts to the point of being willing to die because of them, and yet here you are demanding only second-hand or hearsay evidence from uninvolved third parties because you don’t want to listen to actual witnesses who were universally convinced by that evidence. Speaking of bias.
I suppose you are unfamiliar with the idea of the Messianic Secret. Jesus kept his real identity (that he was God become man) a secret and shared it only with his closest disciples precisely because if he claimed it openly he would have been charged with blasphemy before he could do any actual teaching. This is why he spoke in parables and cryptic language – Son of Man, Son of God, etc.
Besides if you really are interested in independently corroborated claims, you might want to look into the prophet Daniel. Daniel lived around four hundred years before Jesus, predicted the fall of Rome, the coming of the Messiah (literally to the year), the death and Resurrection of Jesus, and the destruction of Jerusalem. Many of Jesus’ cryptic references to himself and to the kingdom of God come from Daniel. And Daniel wasn’t Christian, he was Jewish, so no bias there.