Shield Magic Attack 60%. Where does it drop from?

I've been trying to buy/find this scroll for a very long time. According to hidden-street (which I think is quite outdated), this scroll drops from jonin (which doesn't even exist anymore) or macchu kuchu (same as jonin IIRC). However, although this scroll is rare to find, I still see it in the fm from time to time. I've been buying a few from one particular seller who keeps restocking their hired merch anytime the scroll has been bought with a new one. It's gotten to the point where he makes this scroll ridiculously overpriced. This guy seems to have a way of obtaining such scrolls regularly as a drop. Though I question the legitimacy of that seller, I see the scroll in other shops sometimes whose contents do not seem illegit at all. Any way to get this scroll other than from the gachapon?