As for the matte box, Redrock makes a very good swing-away box that is about a third the price of an Arri or Chroizel.
As for rods, baseplates, and all that assorted voodoo I recommend (now don't you equipment snobs laugh me out of the room now) hitting eBay and searching "Fotga" in the camera/photo category. Fotga is a brand of Chinese-made camera support gear that is SUPRISINGLY good... extremely well made and available in lots of versitile pieces. They have rods, rails/baseplate combos, quick-release plates, and bunches of other parts.
I'm a little bit equipment-snobby myself and I bought a single piece a while back just because I needed something cheap for a one-gig use... and I've since bought several pieces, all of which have been just excellent. Very surprising. For example, I have two very similar rods/baseplate setups for the C300, one from Fotga courtesy of eBay by way of Hong Kong, and one from Zacuto. Is the Zacuto one better? Yep, a little bit... there's no denying they make great stuff. But is it six times better? No, not by a long shot... and that's what the cost difference was.
Incidentally, they also make a swing-away matte box for about $250 (less in some places), but I've never seen it in person so I can't vouch for it specifically.
Fantastic Plastic Entertainment, Inc. fantasticplastic.com