Yes he has been looking but he hasn't found a way. I  mention that on a later chapter too as well as on this one.

"And maybe, just maybe, he could find another way out of this. "

Dumbledore won't give up, and now that he has stopped the denial phase, which is very common, no one wants to face the fact that a son or grandson will die, he is on the phase where he'll try to save Harry at any cost.

I don't know about canon, sometimes I feel like Dumbledore had always planned for Harry to sacrifice himself (that glint of triumph in book 4 shows that he was already thinking Harry would die back then). I don't know if he ever looked for another solution but be sure that my Dumbledore isn't sending Harry to the slaughter that easily. He isn't giving up. Here he was having a private introspection of what would happen if the worst had to happen, if he was left with no choice, who would he choose, Harry or the rest of the world. But by no means is he giving up.

Thanks for reading and the input!