I'll second Wasted Fett. Also check out the Imperial Outpost Armory sale threads in the cargo hold, this is the continuation of RKD armor (which I have). Contrary to what the other poster said, avoid Ebay, Etsy, any other places like that. There are plenty of people out there who sell cheap armor to unsuspecting people new to the costume- whether it be Fett, TK, Darth Vader, etc. It's only later you find out that the armor is inaccurate and cheaply made and needs to be replaced. It's a common story you'll see on TDH every few weeks.
I would suggest keeping your eye on the cargo hold forum, you'll find pretty much everything you need there, from helmets and armor, to girth belts, flight suits, shoes, metal pieces, etc. You'll be hard pressed to find someone on TDH who'll steer you wrong.