The Outfits You Need For The Achievement Are:
Blazer - At The Mass Grave Next To The Beach Cave, In A Coffin.
Camo Suit - Beach Near The Food Bunker, On A Red Canoe With Some Wires.
Dress - Food Bunker, In The Room You Open WIth The VIP Keycard, On A White Couch To The Right.
Gold Armor - In The Residental Bunker, On A Couch In The Living Quarters. (Next Room Over From Katana)
Gold Mask - In The Residental Bunker, Go To The Morgue, The Gold Mask Has Been Placed On A Corpse's Face.
Hoodie - Follow The Road From The Food Bunker Away From The Lake With The Island On It. The Hoodie Is In A Tent At The Cannibal Camp On That Road. I Think A Knight V (Vehicle) Spawns There Too.
Leather Jacket - Rebreather Cave. Follow It To The Right, Past The Turn Off For The Rebreather. (Tunnel Marked By A Boombox In The Ceiling) Jacket Is Stuck On The Ceiling.
Another Can Be Found At The Crashed Plane (Near Maintenance Shaft B) On The Pilot.
Leather Suit - Between Food Bunker and Maintenance A, At The Helicopter Near The Lake With The Island On It.
PJ's - In The Gym Bunker, Go Down The Hallway Past The Room With All The Paintings (And Blood) - The Pajamas Are Sitting On A Shelf Next To The Wardrobes On The Right.
Red Mask - To Get This One Just Use A 3D Printer.
Track Suit - Gym Bunker In The Large Room With All The Exercise Equipment, On A Weight-Training Bench In The Middle Of One Of These Big Rooms.
Tuxedo - Mantenance A Hatch: On A Table In The Bathroom (With The Dead Guy)
Wetsuit - Break Boards To Enter The Shovel Cave, Walk Like 20 Feet In And Use The Rope Gun.
Equip Your Rebreather And Jump In The Lake You End Up Next To.
Wetsuit Is Sitting On A Rock On The Other Side Of The Underwater Tunnel, Next To An Airtank.
Winter Jacket -If You Are At The Crashed Plane (Near Maintenance B) Look For A Nearby Lake WIth Roads Around It. This Lake Has A Waterfall, Look At The Bottem Part Of This Waterfall And There Should Be Two Orange Tents Near The Shore. Winter Jackets In One Of These Tents.
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Its A Total Of 14 Outfits As Of Patch 3, So I Think The Tactical Jacket Also Counts But You Spawn With It.
Good Luck!
(Written Patch 3 of Early Access)