Ok so I'm still a newb when it comes to terms and building stuff but isn't the carrier (LMT) part of the BCG?
There is the bolt carrier, and there is the bolt carrier group which includes the bolt.
If you already have a bolt, all you need is the bolt carrier like this one. http://www.lmtstore.com/parts/bolts-carriers-and-groups-complete/556-enhanced-fa-bolt-carrier.html Note the third hole.