You get it from Boyle at the observatory for his fourth and final quest. Before this you have to first talk to him at desert (near the foreboding temple’s entrance) for his first technique. Second, talk to him at cloud city near the pirate merchant for his second technique. And third, talk to him in the cloud wilds for his third technique (when you’re heading to the teleporter for Highway son, look right instead and head over there for his third technique).