Animated or realistic?
For animated, you really would have to wait, as no one has sculpted it yet. But eventually you would go with KW or WCA armor if it is made publicly available. But for Phase 2, I'd say it's a minimum 3-5 month wait until it's available as the reference only recently became available.
Realistic -- go OSCS.
Either way, you want to register on clonetroopers.net and do some research there. Don't post a WTB thread, as that is against the rules. Search for the terms I just gave you and then contact the appropriate people. But, again, if you are looking to do the new animated look from Season 4, you'll be waiting like the rest of us.
Good luck!
C