Where to get aluminium abrasive powder?
 

Since I don't like the image produced by EE-S Focusing screen.(the ghosting and edge blur problem is really annoying and difficult to solve).
I'm thinking of grinding my own GG.
But I'm not sure where can I find these powder. I don't know which shop to ask for...and I can't find it in e-bay.
And is that I need to add a PCX lens?