Rays Hrdware has more "oddball" ammo than most places. I have bought some there that I could find no where else.
Probably around 2001 or so I couldn't locate 350Rem Mag ammo anywhere in DFW. Stopped in Rays to look and didn't see it on the shelf. Got to talking to the guys behind the counter and told them what I was looking for and he went to the back and brought back 2 boxes and told me that's what they were limiting people to on certain hard to find stuff. It wasn't cheap but they had what I needed.
So even if you don't see it on the shelf, ask someone behind the gun counter.