I'd recommend sintra as a primary structural thing for the 'pack, really. EVA has it's place, but I wouldn't use it for that. Also, Boba's helmet(s) and at least some of his gauntlets were fiberglass, but his armor was vac-formed plastic.
Inquisitor Peregrinus
Because of the nature of the costume (being Cobb wearing Boba’s hand me downs) as well as budgetary and travel needs for getting to Celebration I settled on EVA, but it is very much not a preferred medium for me.