There are a bunch of suppliers out there, I personally can't endorse any "business" because all of my purchases have been from private parties, several found here on GB's,
If you want it fully prepped you'll pay a little more, I prefer to actually
see the primer crimp. This proves to me it is indeed once fired,(1x) and I'll process it myself.
True 1x mimitary surplus brass is just fine. (308-3006-223) Complications can arise if it's been fired through Military Full Auto rifles, many have
huge chambers and the brass has expanded alot. That's not a make or break, it just takes extra care to get back to nominal size. So look for listings that advise it's not been through auto guns if possible.
Mixed head stamp is a pita too, some folks don't care what it is, I prefer to sort my brass at least into the same maker and in the case of LC brass I'll sort into the same years class.
1x is cheaper and Lake City is some great brass.