re: 264 Win mag....

I don't know your usual places, but in addition to Midsouth, I'd suggest checking:
Natchez Shooters
Widener's
Grafs and Sons
BrownellsI
Midway USA

I don't have a 264 WM so I can't vouch for doing this, but what about converting 7 RM brass to 264 WM? They're basically the same case except for the inside neck diameter. One might be able to use a 7 RM full length resizing type S die and the appropriate neck bushing to go from 7 mm to 6.5 mm. That's what I do when making brass for my 20 Practical. The 20 P uses standard 223 Rem brass that I neck size to 20 caliber using a Redding FL type S sizing die, plenty of lube and the proper size neck bushing. I also remove the depriving pin, expander ball and depriming stem. Your reformed brass neck would need to be checked to sure it's not too thick. If you check the internet I bet you'll find something about this possible conversion.
Keep us updated and good luck.