You will have to find the security plans in Fortnite to get your hands on another style for Brutus, on the theme of Ghost or Shadow. After completing 18 of the Brutus Briefing challenges, you will have the option to accept a specific mission for alternate styles.
There are currently three different Secret Blueprints in the game, perhaps. More on that in a moment. They can be found at The Shark, The Yacht, and The Rig. Well, the first two can absolutely be found, the third one which we will discuss shortly.
The yacht
The easiest thing to do to get the yacht's security plans is to go to the front corner, where she faces Steamy Stacks. Land in the water and pierce the side, and you see a door that you can go through. Go down the hallway and you will come to the server who holds the security plans.
Le requin
The easiest thing to do to get The Shark blueprints is to swim through the stone sharks big mouth, climb the stairs, and go through the security door. You can just hammer it in if you need to. If you turn left you will find two server rooms containing the blueprints.
The rigging
To be fair, we have no idea where the safety plans are on the Rig. We searched high and low, and even went so far as to load into a replay and slowly noclip around the whole structure, and we can't find anything. We don't seem to be alone in this area either, and at the moment the location of these plans remains a mystery. However, we're obsessed with finding them, so check back in the future if you're curious.
The good news is you only need to get one, so the fact that Rig Blueprints can't be found at the moment isn't a major issue. After you find them, you'll need to send them to Ghost or Shadow by taking them to a mailbox, and we just have a guide showing the location of each mailbox in the game for now.