correction, I actually put mine in the battery compartment to avoid taking up all my trunk space. It is kinda hidden, but it is located under the white connector and I am pointing to the terminal boots in one pic. In the other pic you can see the bolts coming through into the trunk. There were some other connectors mounted to the back wall like the white one, but I just unclipped them an scooted them down. I don't know your model specifically, but just get creative.
2008 TRX 420 FM
-auxiliary front and rear lights
-dog water and bowl
2003 TRX 400 EX
-Full aluminum skidplates, nerfs, bumpers
-Pro Taper bars & clamps, G2 handguards
-Supersprox sprockets, gold RK