Kids come in many different sizes, and if you are still "kid sized", you'll probably want to go about making it in a rather inexpensive fashion so that it won't be a big loss when you grow out of it. The trash can method will do well. Use a tracksuit or sweatsuit for the flightsuit, repaint a nerf gun or supersoaker for the blaster, and modify a skateboard helmet to look Mando.
chest plates, get the templates and then print them out the size u want. after that get a trashcan (see that thread) and make it OR get plastic sheet o styrine (i know it as PVC sheets) and then cut it out on that useing a dremel tool or what yea got handy. Put in oven for a little on 250 then bend it to body