I know this isn't in the trainer, but the code for this is:
ChangePlayerGkModelFromHumanConfigAndVoiceActor("HumanConfig.9223372049751415851", "dialogactors.dialogactors.sitara")
ChangePlayerGkModelFromHumanConfigAndVoiceActor("HumanConfig.9223372050789760492", "dialogactors.dialogactors.wrench")
You could just edit the trainer and add one of those to the menu. Or just use this edited file here:
Go to WATCH_DOGS2\bin\ScriptHook\data\scripts\trainer\menu
Replace clothing.lua with this one.
Clothing.lua