There is in fact no special way to obtain the P90 within Fortnite. Also, the shell ejection port is moved directly under the thumb grip hole.

The Compact SMG takes inspiration from the FN P90, though it has a longer handguard, shorter rear end with a small stock and the railed frame is moved further from the trigger grip.

The OG-43, designed by Giovanni Oliani in the factory based in Cremona named Società Anonima Revelli Manifattura Armiguerra, was an advanced submachine gun, designed for compactness and ease of mass production.