I found 2 places out here near L.A.
www.surfaceprepsolutions.com is one of them.

Also ask them for their blasting guidelines.pdf info. There's alot of great info in it about CFM, PSI particle mph charts to achieve the best results.

There's gotta be someone out East that sells it too. It's popular with shipyards according to the documentations so I would try calling some places there for a leads. Try sand blaster places too and see if they're familiar with it.

If you can't find it, then try Aluminum oxide. I've used it and it comes out very good with no dust that could piss your neighbors off. Plus save your Lungs from alot of pain later.

I tried blasting with sand once and never again. I was hurting in my chest for 2 days later.