Big Thanks to Shinter for helping me with this.
Locationexplanation Image First Contact (Arena 1) As you enter the first arena, The askjdn, look into the grates on the left side. In the water is the first explosive target dummy.
The Cave #1 When you get to the wall-jumping portion of The Cave, continue to wall-jump without going into the next area. You will find him at the top.
The Cave #2 After finding the previous target dummy, continue through the map using the openable door up top. When you get to the rotating spinners, look back, it is at the top of the bunker.
Gun Range (Arena 2) As you enter the second arena, the dummy is located in the cage at the north-eastern point of the room.
Sewers Before the large density of grappling hooks, and after the rollers there is a cracked door. The dummy is sitting at a table inside this crack.
Exhibit (Arena 3) After going into the Exhibit, take a right, and it's under the scaffolding.
Tower (Finale) Before going into the ending credit, look back!!