Avete!
Deepeeka is the only place making "off the shelf" stuff right now, and I'm not sure which of their early-era pieces are usable. They did improve their triple-disc pectoral a lot! Their Attic helmet could be better, but could be worse. Their newest Montefortino looks great in the pictures but turns out to be HUGE. Nice fit if you're Goliath.
Hadn't seen Armillum before! They've got a lot of Deepeeka stuff, but also some stuff which looks much better! I like their Republican scutum, and most of their belt parts look great (except that pugio frog, hmm...). (Deepeeka's belts range from "not good" to "doo-doo".) Still mostly Imperial era gear, of course.
You'll probably end up having most of your stuff custom made, by Manning (he's great!) or someone else. There just isn't any place mass-producing any of it.
Where's Danno the Samnite? He's working on the same kind of impression (though last time he turned out he borrowed some of MY gear!). A couple of us in Legio XX have some Republican Roman gear, but I need to get better photos of it all. Some is on our Photos page or Roman Days page:
http://www.larp.com/legioxx/photos.html
http://www.larp.com/legioxx/rdays.html
Best of luck! Fascinating era. Keep the questions coming!
Valete,
Matthew/Quintus, Legio XX