Don't get him a plate carrier.
The Guard will issue him one (or a vest), with plates. He'll never need armor for Cadet training (the FLC you see him wearing at contract swearing is what Cadet Command issues ever'body). Once he commissions they'll issue him one from CIF (the Central Issue Facility).
LBE can be personal, and he'll more than likely figure out on his own what he wants and needs, and how he'll configure it.
Since you're in Carolina, the best I can offer is -- drive up to Fayetteville/Spring Lake. There are dozens of cut-throat surplus stores there that compete with each other to sell gear guys have stolen, found, or were issued and told to keep when they separated, retired, or went AWOL -- plus all the retired gear the Army sold as surplus when colors changed. GWOT was Command Sergeants Majors' nightmare when it came to mixing kit in OD, woodland, tri-color desert, ACU, khaki, brown (coyote), and multicam.
You'll find in some shops you can negotiate pricing on stuff with a couple careers' worth of life still left in them if they're not in the latest color or unique SOCOM items ARFers, airsofters, and LARPers want.
I'm a gear queer, and my son (now a lieutenant and also a geardo) and I personally like Sarge's in Spring Lake.
If, after all that, he still doesn't have what he wants, then buy off the EE or new. SKD, OPTactical, and other arf sponsors are great.