Let me make sure I completely understand!

You can buy:

Bertram brass from HSM/I.Q. Metals - Bertram 408 Cheytac Brass

"CheyTac" brass from CheyTac - .408 Brass Cases | CheyTac USA, LLC

As far as "Lost River" and "brass". I was under the impression that "Lost River" was only known for projectiles (Midway still has a page for their "408/419 gr - discontinued"). The Manta listing for a company by that name - and with their long-ago-abandoned website - lists a company in Idaho. I just tried the listed phone number and it is no good ("...cannot be reached as dialed..."). Please provide contact info.