muahahahaha the game hasn't released yet, so unless you have an in over at Bioware good luck getting the game models.
I've been working on a SWTOR BH for awhile now and it's slow going.
The concept art doesn't transfer well to real people.
He can pretty much forget that for a budget as tiny as that.
Heck my Helmet is about his entire budget and it's not finished, nor do I have the lights for it yet.
There is a Lady here on TDH doing a female SWTOR BH I believe and she has sunk way more than his budget into it sofar.
There is also a Gentleman here that did a bangin' SWTOR Bucket and he tried to sell it awhile back for around 250$.
For a hundred bucks and good quality you are looking at a LOT of sweat equity.
The old adage holds true: Fast, Cheap or Good. Pick two.
What you could pull off is a Custom Mando, Pep'd TK or CT.
Mind you a GOOD Custom Mando will run more than a 100$ unless you build/sew virtually all the bits yourselves.
What do you have tool and skill wise?
Start cruising thrift shops and surplus stores now, cheapest places to get coveralls/flightsuits, belts and leather skirts/jackets (for taking apart and re-sewing).
If you do a Mando You have the benefit of excellent build resources, both here and at the Mandalorian Mercs board (both free), Wizard of Flight's most excellent Templates (free) for helmet as well as Armor and plenty of tutorials for sewing the softparts.
If you do a TK or CT scratch build You'll have to look and shop around for Pep files, there are free ones out there but your mileage will vary.
If your son insists on SWTOR, I'd suggest the Trooper.
If you look real close the individual armor pieces are mostly Clone or Storm Trooper pieces with a few others thrown in for good measure.
Some pieces are unique and you will have to figure out how to make them yourself.
Again the Bucket will be ... interesting ... to build, but if that's what he insists on...
You may have to redo it a few times to get it right, fit and look.
Cruising places like Whitearmor and CTN may help you here when it comes time to attach it all, as it's essentially the same armor with a different look.
You could try to find pep's for the pieces you can identify and use the others as base pieces to modify for the ones you can't identify.
This project will take alot of time, you may run short even starting now... Darth Real Life will show up atleast once before CVI.